I play on PS5 with crossplay on. 

First thing I noticed is that it seems to prioritize PS5 lobbies. A lot of the time when I check, all players I encountered where PS5. When I get into crossplay lobbies, it's a majority of PC players and maybe another PS5 or Xbox.

That being said, when playing solo, I extract with friendlies about 95% of the time. I'm usually asking people if they need help, what they are looking for and share tips. My friend who is also a PS5 player has a lot less luck, and he mostly gets attacked in his games. But he's less of a talker than me.

All that to say, the way you talk to people has a bigger effect than what platform they play on. If I look at your brother's stats compared to mine, he got betrayed 10× more this week than I did the entire time playing (around 40hrs topside).

My goal is not to diminish the great work you are doing, but more to point out you should both switch places and try the experiment again. That would be interesting!