I think you guys need to see the bigger picture. FF 13 and 15 were not incidentally a part of a plan, laid out through internal emails & documents, to spend Sony out of the market through targeting their closest 3P partners for acquisition. They were not a means of buttressing Square-Enix into eventually preferring them as a platform holder for marketing deals and release priority (if not later on acquisition).
It's becoming increasingly obvious that Microsoft is looking to turn Square-Enix into another 3P ally of theirs the same we've seen with Sega/Atlus-Sammy. Who would've seen the results we've seen now, coming back even two years ago? And, Sega/Atlus are one of the other big Japanese 3P publishers Microsoft have expressed intently wanting to acquire.
Nothing really "prevents" them from buying a Japanese 3P publisher BTW; they just can't do a hostile takeover is all. But companies like Sega/Atlus are not under a "protected" status, so if they want to sell, and Microsoft wants to buy them...well that's that. The same pertains to Square-Enix. The previous Square-Enix management may've been considerate of deeper partnerships and/or acquisition by Sony, but the new management might not be within the next 2-3 years when Sony's supposedly finally ready to make a move.
By that point, they may be more willing to stay independent and do partnerships with Microsoft. Which, hey, ideally I'd love if ALL 3P pubs stayed independent, but realistically that ideology doesn't hold up considering some of the moves MS have already made to remove 3P options from the market, expressed intentions of doing more (and targeting those close to Sony on top of that), and their endgame in this.
I'm telling you, this renewed relation between Square-Enix and Microsoft is NOT like the previous ones; I think it's going to take you and others by surprise and much of this can fall at the feet of Sony's hubris.
Why would they use a picture from a game that isn't on their platform?
The only answer is: it's not on their platform...yet. But it's very likely on the way. Circumstantial evidence would back that up.
Otherwise if not...then like I've said in the past, Microsoft should be investigated for marketing disinformation, astroturfing, and so forth.
They can but they don't seem interested or are just LTTP at this point. There's something to be said about securing your legacy, especially in terms of optics perception among the enthusiasts in your customer base. Sony have been very poor at recognizing this and being proactive on it.
While this ABK BS was going on, they should've been starting and getting deep into a mix of 3P dev/pub acquisitions, share buys, and investments of their own. Maybe give a word or two about not necessarily liking the ABK acquisition but, it really wasn't seemingly worth all the effort & attention placed on it at the end of the day.
Now it feels like they're trying to play catch-up in that regard. Not a good spot to be in, regardless who you are.