The official Matchmaking blog post

@Axs5626Sxa5001It isn't that high MMR lobbies exist, it is that MM seems to put me in them or it drops those players into my lobbies when the MM timer for them goes off. Premade just makes it 500% worse, too.  My brother and I (both probably Gold players at best) play as a premade duo in Trios pubs and struggle to get kills for hours at a time and the MM does absolutely nothing!!!  We've played together off and on for about a year and have maybe 5 wins.  Our KDR playing together is probably half what it is playing solo.

Got killed by somebody last night with 10x the kills, damage, & wins as I have and pred badges all over their frame. I was juking all over the place and he basically killed me with 4 Wingman shots. Then he killed the other 2 in our squad just as easily. That is like showing up for pickup basketball at the YMCA when the Golden State Warriors got next. Screw that, I'll just hit the weights and go home.

Update 5/23:  I'm now in the camp for just scrapping all SBMM and making pubs matchmaking "first come, first served".  This crap is horrible.