Nobody's going to compromise a release on behalf of the Steam Deck, that's on the user/Valve to figure out how to get it running well enough. No console-like cert process, just an after-the-fact verification model. But yeah, the architecture does line up much more closely.
I meant the comparison in terms of the types of sacrifices that will be made for certain console games to run on the Series S. There are some remarkable ports on the Switch (Doom, The Witcher 3) and they're playable, but still fairly compromised compared to what the Xbox One/PS4 versions of those games were like. The Series S could end up in a similar position relative to the PS5/XSX, depending on the game.
Like, right now the most consistent difference between playing games on Series S vs. Series X is resolution, and reaching towards 120 FPS (which some games still pull off on the Series S performance modes, I believe Samurai Shodown does for example). That gap could widen a bit for some memory-hungry games. But I think both will still be playing fundamentally the same games.