Yeah, MS screwed up by not giving the XsX GPU a bit more juice to essentially double the One X each time, every time.
Imagine if that were the case. One S is so far behind that running those profiles is a total kick in the nuts to,what is an awesome feature.
all they need to do is to figure out how to either:
A: Lower the resolution on FPS Boost games that have issues, without going all the way to the One S version.
or
B: Lie to the game about the framerate it is currently running at. Dynamic res games will not lower their res as long as they don't drop below their original framerate target. so a game like Titanfall 2 will try to run at 6k (which is apparently the upper bound on One X) until it drops below 60fps. that is a huge issue when FPS boost is introduced. so they would basically need to find a way to give the game fake data so that it thinks it drops below its original framerate target even tho it is acually running at 2x that.
in order to run some of these dynamic res games at 120fps would currently need WAY more horsepower than 2x of the One X. 6K120fps is WAAAAY above 2x of what the One X can do, even 6k60fps is way more than it can do, it only ever reaches that res if you are in a super low stress situation an look straight to the sky or something.
just a bit of maths with Titanfall 2 as an example of a dynamic res game.
Upper Limit: 6144x3160 60fps (1.164.902.400 pixels per second)
Typical Perf.: 2666x1500 60fps (239.940.000 pixels per second)
(no exact numbers but in the ballpark of what Digital Foundry etc. found)
Series X would only drop below 6144x3160 if it goes below 60fps. so in order to play it at 120fps in One X mode the Series X would need to actually push the full 6k resolution of the original One X version...
so for FPS boost it would need to push 2.329.804.800 pixels per second... that would need 9,7x of the horsepower of the One X