It's happening here too.
Tav game started on PS5, syncs from PS5 to Larian, and Steam downloads from Larian.
Origin game started on Steam, syncs from Steam to Larian (I suppose), but PS5 doesn't download it from Larian.
It's cross platform from PS5 to Steam, not the other way around. I haven't tried to change that game on Steam to check if PS5 would download newer save from Larian. I suppose it could work, but I won't create a new game just to try.