why is not using the dll the "hardest way" to implement it?
and maybe they thought the best way to implement it properly was a fully dev driven implementation that is finetuned for this game, and the way to do that is to lock it to a specific version that looked and worked the best in their opinion
also, thanks to PC Gaming Wiki I now have found a few more games that support XeSS and DLSS but not FSR2/3/4
AEW Fight Forever
Chorus
Deadlink
Dead Take
Deceive Inc
First Dwarf
Flintlock
Fortnite (it has TSR of course, but no FSR4 so far)
Ghostbusters: Spirits Unleashed
and I stopped going down the list at that point, but alphabetically on that list from A to G, those are the games that support XeSS and DLSS but not any form of FSR.
afaik. none of them were Nvidia sponsored, and if they were, XeSS somehow still made it in.
I also saw a few games that only have XeSS support in there, which is weird, but...