Originally posted by avatar.zero:

The "crossplay" option just means turning on the Microsoft multiplayer component. On Steam, it's optional since you can still do multiplayer openly without having to deal with Microsoft if you don't want to. On Gamepass/X-Box, it's required since ...

I assumed the same but refrained from answering because I've never played any Gamepass/X-Box stuff. -> How do you know that / what's your source? (just out of curiosity)