the game engine makes the hard work an how and where use upscaling, but drivers affect a lot of image postproduction and how to accelerate the fsr! And both of those affect how the game looks like.Strange article. Because FSR seems to be almost hardware agnostic, it is most likely that there is no need for any kind of explicit implementation. If you want to use it, you most likely can as long as your GPU is fast enougth.
Additionally Raja only answered to an direct question if FSR will be seen on Xe. It is also possible that he only was polite, because according to leaks Intels seems to work on something internally called "XeSS". Only time will tell ...