Of course it's true, I work as gamedev since almost 20 years ago and know many people who are working or worked in many places ranging from top AAA to small indies (an a few examples, the ones running a studio that back then only made handheld games for Sony and whose feedback contributed to how Vita was, or the one running another that only made games for Nintendo portables until needed to go multi the previous generation), so I know the costs and the reasons of why many of them don't support Nintendo (or moved to multi), portables or even in the case of Sony why they did stop supporting portables.
Since decades ago by definition PC (unlike console) games have been scalable, but modern PC handhelds are the first ones to have horsepower enough to be capable of featuring basically all current day big ass AAA games. And more importantly, without needing any porting job.
Any home or portable console with a dedicated OS, even if like PS or Xbox they essentially feature PC hardware, only works with its own dedicated games and ports. Even if has similar hardware to PS4 or PS5 but with really minor changes. Meaning, resources or money. Not in the case of a PC handheld, because the PC ones would just work there.
I'm a gamedev who worked in over 40 published games, who is now working on a Game Boy game, a VR game, a PC+console+mobile+arcade game, a console+PC+arcade game plus mentoring multiple external indie games. You're the one who has no idea what you're talking about, not me.
Yes, there's something cheaper: what I said, to don't need to port it for a handheld because those handhelds basically have hardware equivalent to current popular PC destktop hardware and passes the typical minimum PC specs of the games. Meaning, a PC game that runs decently enough in low/mid tier PC desktop hardware specs just works in these portables.
The only thing that the game needs is to support gamepad controls and to have a minimum text font size big enough to be readable in those screens. No porting or extra optimization required.
Nowadays almost all companies (including MS and Sony, being Nintendo one of the few exceptions) already port their games to PC because the desktop PC is a big enough market they need, and the PC handhelds are a submarket inside PC. They don't port a game to PC to have a handheld version: their business is PC as a whole, mostly desktop. To get the PC handheld version is something that is essentially free when having a decently scalable PC game.
The reason of why Sony doesn't leave their consoles open is because they want a revenue cut from all games running there, so they don't allow other stores there. That (with a small extra help from PC and mobile via other stores) they have enough revenue and profit. But they will want to continue growing, so at some point they'll want to have their only PC and mobile PSN stores.
And once they open their PSN stores for PC an mobile, they'll want people from these platforms, including those in the different PC handhelds, to buy their games there.
I assume initially will want to release their PC handheld only featuring their own store/games, but I think that whenever their release their portable (maybe 4-5 years from now, around a year after PS6 release as PS Player next gen successor) all the other PC handheld competitors will feature multiple stores and OS, so to be fully featured Sony will end -maybe after launch- allowing to install other OS.
PC is a bigger market in terms of userbase and revenue than PS, so it has more value.
Specifically for Sony, PS is an already huge market for them and doesn't need extra help, meanwhile their PC business, despite being very profitable and to keep growing very fast, has way more room and potential to grow.
If a first generation of that device gives them let's say 10-20M new users that would mean a bigger % increase for their PC business -just because it's smaller- than to their console business.
On top of that, in a few years pretty likely PS will have the home console market basically just for themselves, with almost no competition, with Nintendo focused mostly on handhelds and MS full multiplatform leaving their console hardware mostly to 3rd parties. But instead in PC they'll have a lot of competition of many stores, for 3rd parties mainly Steam.
So it would be smarter to use that potential handheld to support more directly their growing PC business because it would need it more than their console business, which already mostly reached its full potential.
Sony and the 3rd parties know that all non-Nintendo portable consoles, with PSP as exception, failed to generate a big enough market to make games and ports profitable for them. In case of Nintendo devices, their 3rd party sales since the N64 have been too small for many publishers to fully support them with their AAA games.
PC handhelds don't have these issues of needing to generate a big enough catalog and userbase to make their games or ports profitable, because their games and stores aren't limited to them: they are normal PC games, and these publishers and storefront ownsers already are already happy with their desktop PC business, handheld PCs are just an extra for them.
Having the games catalog and profitability issue sorted indirectly with the desktop PC market, PC handhelds manufacturers only need to focus on keeping hardware side sustainable and reasonable: not too expensive to make it appealing to the biggest amount possible of players, not too cheap to avoid losing a lot of money per unit.
In the players side, being PC means they have a huge catalog: they don't have the issue of portable consoles not featuring enough games, including most of the most popular ones like GTA, FIFA, AC, CoD and so on: they'll be there.
Portable PS4 and PS5 hardware are they fiction here: they don't exist, would be too expensive and would require dedicated games/ports like the Vita or Switch because the hardware can't be 100% the same.
PC handhelds aren't a fiction, they already exist and feature most PS4 and PS5 games. By the time Sony would release their next portable device (maybe 2027-2030, around PS6 launch or a year later or two?) they already will have ported to PC all their PS4 and PS5 games -plus some PS3 ones- that they consider with potential to continue selling decently in modern times.
Do you know how you can tell that your argument is ridiculous and without merit?
Make the exact same argument for Sony making a PC based console and see if your argument holds up.