Yep, cause you're also getting the extra EXP from friending.
I don't think anyone who is bothering to make some smurfs and playing against people at the 1700 level is too worried about improving at the game as most everyone they play will either also be smurfs of wildly varying MMRs or actually new. There's not much you can improve when you have a year of game experience playing absolutely green players.
If anything, in the case of folks like Milly who are far higher MMR, when they enter QM they are making everyone else's games worse by being a 3k + player in games made for people with half of that MMR.
Basically every game feels like you're playing AI mode, except with the added frustration of toxicity, player's general newness/cluelessness, and the all too frequent disconnects/quitting that occurs in the new player range. You can't ping 1600 MMR Thrall and Hammer + the two others to follow you to protect anything or to end the game. Well, you can ping for them to, but the results vary. In AI you can make them. Sure Milly can carry pretty well in HOTS at that skill level, but he has to contend with all the other shit too.
I'm not saying AI is for everyone, but it's definitely the path of least resistance to getting this done quickly. There's no BS and no queue times to contend with.
The grind is mindless either way you do it. The AI method just makes it truly automated so you don't have to deal with herding the cats.
It is several orders of magnitude more fun to style on pubs than it is to style on computers.