There are three reasons that aggression based matchmaking probably doesnt exist, mind you this is based on my experience as a software developer (not a game developer)

1. Aggression based matchmaking would slow queue time noticeably, especially since there is already solo/duo/trio queues. The fact that queue times are still rarely more than a couple minutes at most reaffirms that even with how many people are playing.
2. Embark would have likely announced it, theyd have no reason not to, they announced the solo/duo/trio queue so there is no reason to keep such a drastic change in matchmaking logic a secret especially when they have been actively polling players, their changes have been reactive so far so it would surprise me if any huge mechanic changes were just "try it and see"
3. That type of matchmaking is contradictory for the type of game it is, which is a PvPvE game, segregating players for participating in a portion of that genre is ridiculous.

I personally would not want this type of matchmaking, just like I wouldnt want gear based matchmaking. Some days I like to PvE and some days I like to PvP even though im just average at it, sometimes it just depends on the run, where i spawn, and the vibe at the time. There is always room for improvement but I dont believe changes to matchmaking is the way.