The game wouldn't have sold much better on Xbox if it WAS Day 1, let's just be honest about this for once. It's not like SE don't already have historical sales data of other FF games that were Day 1 on the 360 (XIII) and XBO (XV), which likely influenced them into going with SIE for exclusivity deals. If sales were solid on Xbox, they would've rejected the exclusivity deals with PlayStation.
Also FF's problem ATM isn't platform availability, but a lack of consistency in its identity. Massive gameplay changes between installments, being a likely major factor into this. They're also paying a price now for mistakes made way back in the PS3/360 era and then again PS4/XBO gen with XV. Rampant delays, huge changes in scope, and a XIII triology that didn't end up feeling like a cohesive trilogy with a satisfying answer chipped away at goodwill in the IP among the faithful.
Which in no doubt played a part in XVI's reception (fueled in part by that game's own divisiveness) and perhaps even Rebirth's (maybe more people are just choosing to wait until that trilogy is complete before jumping in). Xbox Day 1 isn't going to "save" anything when it comes to IP like Final Fantasy. That is one fantasy worth letting die.
The sales wouldn't be much but it would be more than what it currently is which is nothing. Square Enix needs to build up a fan base on Xbox and they can't do that if half the games are skipping the platform because the consumers you do get, you're going to lose them and not gain anyone either. Also, people need to be honest about PlayStation as the games barely sell there too. Unless it's a Hogwarts, COD, a top tier major Sony IP, what sells on PlayStation? People brag that FF XVI sold 5m copies acting like that's great when in reality, it's shit because what happened to the other 55m console owners? They said fuck that game.
PlayStation fanboys/extremists overhype sales on their platform like it's hitting Nintendo level numbers. LMAO. Seriously, it's a fucking joke. Look at all the games that release every year. Excluding the annual IP's like COD and sports games, what truly sells 10m+, 20m+? Almost nothing. You'll get a Sony main event here and there, you'll get an Elden Ring type game and Hogwarts Legacy but just this generation alone, how many games have sold anything on PlayStation? It's like a handful of games out of hundreds that have released on the platform. Consumers/gamers just aren't buying games like they did last generation and this includes on PlayStation. They'll buy that one or two major game releases a year and that's basically it outside of the annual games that they normally play. Add in the higher price point of entry and yeah, it becomes even less. It's a reason why majority of games are still cross-generation because publishers are not seeing and getting the numbers they want on PlayStation.
And yes, the same can be said double if not triple for Xbox. It's all about building up the IP and the best way to do that is by being everywhere (PlayStation, Xbox, PC via Steam and Epic and Nintendo if possible), not by limiting the potential consumers that you should have access to. You're not getting everyone obviously but you'll get way more people on various platforms day one overall as opposed to if you stagnate the release. Stagnation ONLY works for the hardware manufacturers. Doesn't work for the publisher or gamers/consumers. It just doesn't. Especially now when games are far too expensive and everyone wants better graphics and visuals which costs a shit ton of money and doesn't guarantee results either.
Sega went full third party and are staying that way because they're seeing results. I bought Lost Judgment on Xbox because it was available day one. Will do the same for Pirate Yakuza which looks awesome by the way. You can't get people into your games and IP's if they're not on the platform. Too many people here make it out like PlayStation is the savior when in reality, all they're doing is contributing to killing off third party publishers, their IP's and their games because while getting FF XVI and the Remake trilogy is great for them, it does NOTHING for Square Enix and considering the fact that those deals were signed a decade or so ago, looks far worse now because costs increased dramatically.
I can't comment about all the previous games in the series since I didn't care. Remake was the game that got me interested in the franchise. FF XVI is a great game in general but yes, it's a disappointing Final Fantasy game because the RPG elements are literally non-existent. If it was a spin off like that Stranger game, it may have done better instead of being a main line game. Also, Square Enix lack of awareness when it comes to releasing their games is comical as you can look at Fall 2022 as a perfect example. They released like 10 games or some shit like that in a four month span which is crazy.
I never said Xbox would "save" Final Fantasy but if Square Enix wants the IP and fan base to grow, it has to be everywhere day one, not just PlayStation OR Xbox. Once you skip a platform with a single title, you're pretty much killing it off on that platform because those who did care won't anymore and you're not going to get new people because they can't trust the publisher that the next game will be everywhere day one. So when you combine those factors as well as the majority of PlayStation owners themselves not giving a shit about the games or IP itself, well, it's a recipe for disaster as is pretty evident by Square Enix own admissions.
Third party publishers should release their games everywhere because it's not about just the sales you get, it's about the growing the IP which long term wise will always be far more important than a one off sales wise. You can't grow it or get people interested in the IP if you're skipping platforms completely or stagnating the release. Those people will just go elsewhere.
The best way to make Final Fantasy bigger and more popular is for the IP to go away for a decade and then come back everywhere with an amazing JRPG, not an action adventure game. Then you'll get way more people because first and foremost, the game would be available everywhere and second, people can't miss or want something if it's not gone for a while first. The appetite for a new game in the series would be there. They have the third part of VII which is probably 2028 if I had to guess. I wouldn't release FF XVII until 2032 at the earliest. Let the man series go away for a while and then come back with an excellent JRPG.