An official EA thread is full of complaints. There are the same issues with no anti-aliasing and blurred or jagged edges around players. Apparently, menus on the S function at 30fps compared to the X’s smooth 60fps. In the thread, EA community manager EA_Aljo responded in the following post:
Hopefully, this gets resolved soon for players on these systems. Let us know if you have been playing on Xbox Series S and have been experiencing issues below!
Our own community has reported that some faces can’t be bothered to make it to the pitch with the rest of their player’s heads, while their bad looks have been reiterated on Reddit forums. Both the issues suggest that EA has poorly optimised the Series X version of the game for Series S. Online lag on Series S that is not present in the Series X version is a humongous issue for some, though there are fewer reports of this particular issue. Not just in the popular FUT mode, either, but in Pro Clubs, Volta, and Seasons. It seems like the FIFA 21 Series S version was in a similar state, and remained unpatched through the year.
“Hello, everyone. We’re still investigating this issue and will provide an update as soon as we have one. It’s most definitely not being ignored. We’re trying to get this resolved as quickly as we can. Thanks!”