There was a recent game announcement that was Amd sponsored that has both (I think it was the avatar game?). I think it's very likely many of the games are time or budget constrained, and so when they're given money from AMD they implement that first and if they've got time or previous code add DLSS.
This feels like the old console money that Sony & Microsoft would give where developers focused some extra optimization or early engine design around one platform because of extra funding. If I recall, Sony gave a bunch of money to xplatform games.