Ya, but MM is supposed to be randomly creating these games, so highly unlikely that he will play 20 games in a row that are above his ELO. Random games means that he will sometimes be over and sometimes under the average ELO of the game.
Even if he gets 20 games in a row with a higher ELO (again unlikely) then winning 10 and losing 10 means he deserves his ELO to increase a lot more than decrease. He didn’t break even at his level, he broke even at games higher than his ELO by 300 on average. This is not the problem with current ELO.
Many of us have noticed that we gain more points upon winning on average, than we lost upon losing on average. There lies the problem.
Another issue I hope devs would resolve when they (eventually, if ever) work on fixing ELO, is to make the starting/average ELO the same for 1v1 and TG. I can’t count how many noob games I got kicked out of, because the hosts get scared of my 1500 TG ELO, though it is the same as ~ 1000 ELO in 1v1. This is annoying.