I'm aware that Destiny, and many other games, have cross play between multiple platforms. Hell, Destiny is the main game I play. It's obvious with context that I was talking about Outriders, answering your question that was also obviously asking about Outriders specifically. But let me spell it out for you
OUTRIDERS ONLY HAS CROSS PLAY BETWEEN THE XBOX AND WINDOWS STORE VERSIONS.
OUTRIDERS ON STEAM HAS NO CROSS PLAY WITH OTHER PLATFORMS.
OUTRIDERS ON PLAYSTATION HAS NO CROSS PLAY WITH OTHER PLATFORMS.
Clear enough for you?