It can lead to PS4.8 being able to play a game that was originally designed with the intent of it being for a high end PC, and when they see PS4.8 can run it, they decide to port it over. While on Vanilla PS4, it would run like garbage.
In that case what do they do? Only release it for PS4.6 and PS4.8? Not release it at all for PS4? Or water down the game even though the original intent was for it to be a PC title, just so it can work across all versions?
You are totally fear mongering man.
PS4/XB1 are closed platforms. Sony and Microsoft can enforce requirements on games launched on their platform that they have to be compatible with all SKUs in the PS4/XB1 family (foward compatability). Hell, Sony can even enforce these limitations via the API, by not giving developers access to the acceleration hardware outside of control over the frame rate lock and resolution (they can cap it at 1080p to limit your concerns).
4K upscaling just occurs. If the game is sent to the OS at a resolution of 900/1080p, and the device does the upscaling on its own, your whole cocern is moot.
I was replying to your question about why someone would be concerned about this. Fearmongering is when you are deliberately trying to spread fear.
What's the difference between expressing your own concerns about something to someone, (especially when specifically asked by someone to do so) and fear mongering, according to your definition?
And yeah, what you're saying about enforcing requierments falls under my "Not release it at all for PS4?" comment. It can be decided by the publisher or the console manufacturer for whatever reason. On the publisher's side of things, being forced to accomodate to such standards may be a negative thing, because it's not just a situation of "if the PS4.8 didn't exist, they wouldn't consider releasing it on the PS4 in the first place." This depends on how far Sony/MS plan to take this. It could lead to a longer "concole generation" than we're used to. So at a time when we would normally have a PS5, we may instead still be on PS4.8.
But on the console manufacturers side of it, they haven't always made that choice. In recent times, there's Xenoblade for New 3DS. It only works on New 3DS, mainly because of the difference in RAM, iirc. It would run below Nintendo's quality standards on the other 3DS models, so Nintendo decided to only release it for New 3DS. And in the past, we have some examples on the N64, where certain games (Perfect Dark, Zelda Majora's Mask, etc) only worked if you had an Expansion Pack.
So that something like this could happen isn't unsubstantiated.