Robert is talking out of his ass. The difference this current gen has not been that big in comparison to next gen. You are talking about 4TF vs 12TF and a significant change in RAM speed.
This aint no PS4 vs PS4 Pro difference we are talking about.
Unless you are a developer like him, I will take his word over yours. The X1 to X1X was a 4.3x difference in raw graphical performance (not even bringing into account different GPU rendering technologies, a 5.3x RAM speed deficit and faster CPU) and basically ran games mostly the same apart from resolution and texture quality
The XSS and XSX have the same CPU with similar speeds (much closer than X1S and X1X, also both close to PS5), only a 3x GPU performance deficit with all of the same GPU technologies supported, only a 2.5x deficit in RAM speed (for a GPU supposedly targeting a resolution 2.25x lower than the XSX) and existing games are already seen to be working well on both systems.
PC hardware scales between resolutions in very similar manners. The games will run perfectly fine on XSS at a resolution between 1080p and 1440p at the same frame rate as XSX running the game at 4k. Some settings might be different, but the games will be fine