The Series S is something else.... thats not being fair to the Xbox Series X. It sacifices alot more (the S), in basically every mode.
The thing is, I wouldn't be surprised if Series S does indirectly impact Series X experience in some cases.
Expecting fully equal optimization for 2 Xbox SKUs just seems unwarranted by Xbox marketshare vs PS5.
(smaller marketshare should justify less optimization for just 1 SKU, even before being split into 2 SKU)
MS designed them to "scale" well (1080p/4K) but if S and X have own unique bottleneck for given game,
constaining both by combined sum of BOTH bottlenecks may be needed to get 2 versions on same budget,
even if that means a given version is being constrained for a bottleneck that doesn't actually apply to it.