We finally know for sure... Embark has confirmed that they're using aggression based matchmaking for the game, so PvE (more friendly) players can get more friendly lobbies, and PvP (more aggressive) players can get more fights (and not feel bad about them).

It's great, because everyone gets what they want instead of driving off PvE players by incentivizing PvP players to relentlessly hunt them.

www.pcgamer.com/games/third-person-shooter/arc-raiders-contentious-aggression-based-matchmaking-isnt-just-smart-but-absolutely-necessary