There's a really big difference when it comes to desktop games and handheld games. This is because of its game size, quality, and if it's a multiplayer game. These factors will change the format, that's why other games can be played only for desktop and not on handheld gadgets.
I have already noticed that. Not with Duckstation, but other emulators that have problems with making settings in SteamUI, for example, because another window (eg folder selection and access) would have to open, but the SteamOS sometimes has problems with it. For me, in mGBA, the attempt to select a file in SteamUI leads to a crash, in desktop mode simply opens in window to select the file and everything works.
I hope that such problems will be fixed in the future.