OK, i agree that party size should count on the decision but i also understand that this is suppose to evaluate the aggressiveness of a player. Since you play very differently solo and trio you probably assume everybody does.

There is some truth IMO on saying that many aggressive players will be just the same irrelevant of party size. The more chill solo is something that appeared organically because people wanted at least one safe space. But it’s not really a rule or anything official. I personally wish I could play trios in a more peaceful manner so I agree the change you suggest might help. But also people that are aggressive will often be on any modes anyway. I find hard to believe the extract campers in trios would suddenly be any different when they play solo…

Also in trios the matchmaking has to assess the aggressiveness of three players and find and adequate lobby with other similarly aggressive teams. So it’s not as simple as having three hidden MMR aggressiveness because I think people tend to naturally be more aggressive in groups. So a group of mildly aggressive players can be a very aggressive group when they free loadout on stella montis ;)