Why Are They Putting Teams Vs Randoms in Mixtape?

Has anyone else noticed this? Literally every match now, there will be at least two stacks of 2 each, often one 3 stack, versus a bunch of randoms on the opposite side. Talking for deathmatch and control. I queue solo, so I don't understand why I'm on the random team instead of paired with one of the 2 stacks. Why put all of the coordinated groups on the same team?

These aren't unexperienced teams, either. They're always at the top of the charts damage-wise, though they may be smurfing in some cases, but not all.