I'm pretty sure there's no skill based matchmaking or team balancing of any kind in Trials (other than whatever is going on with card win matching that may or may not still be happening). As long as Trials is a tournament style thing, it has to be that way otherwise there would be incentive to game the system to fall into certain skill "bands".
Yes, it was Trials.
I get why they don't have SBMM in Trials. I'm actually okay with that. What I'm NOT okay with is a lobby-based teambuilding algorithm that says "Okay, we have these 6 players, how will we divide them up into two teams?" and decides that "Let's put everyone with an ELO above 1800 on one team, and everyone with an ELO below 1000 on the other team" is a good solution. (It wasn't quite that bad. I had an ELO of about 1200 at the time... but I was teamed up with an 800 and a 600... with the other team all a minimum of 600 above ME (one guy in the 3000s).)