you can use FSR on Nvidia too but you can't use DLSS on AMD. Nvidia has been trying so hard to force a monopoly for decades now with these features they lock down to not only their hardware but specific series of them.
it's reminiscent of Microsoft making sure Linux can't use a wide range of software via directx and such, forcing people to resort to WINE and effectively becoming an operating system monopoly outside of apples gated garden
meanwhile AMD let's everyone use their software tech and people cry foul the moment they do 1/1000th of the anti competitive behavior Nvidia does in its sleep, I mean this is literally just sponsoring a game
Nvidia literally refuted this argument and come out and say they don't force devs to leave out FSR. DLSS workshop also includes tools for devs to put FSR and XeSS in their games along with DLSS.
Where as AMD responded with PR bullshit and fuckall.
This usually means only FSR, no DLSS. What does it matter that FSR can be used on all hardware, if it's the inferior technology? Let those who can use DLSS, and others FSR and XeSS.
Since it's your mom-and-pop multi-billion dollar company, it's fine that they screw over consumers. They are not like the evil multi-billion dollar company from down the road.