Taking to Twitter, GSC's Slava Lukyanenka said that "something glitched in my head" during the Gamescom interview, and the dev actually meant to say 35FPS instead of 25. Slava says that the team is aiming for a minimum of 30FPS across the board on Xbox Series S.
This sounds much more like it, and if the studio can get a consistent 30FPS out of Stalker 2 on Series S, we'll be quite impressed. This is a massive, technically advanced Unreal Engine 5 game, so it's bound to take some running on any console - let alone Xbox Series S.
We also have a couple of months left for the team to keep polishing up Stalker 2 for its Xbox Game Pass release. The open-world FPS hits the library on November 20th, for Xbox Series X|S and PC.