I wonder if the MMR gets stuck to the highest of the month

So I’m doing these achievements in wild with a butchered highlander deck (no reno); at some point I’m saying OK I won a little so some wild players start getting in with netdecks making it hard to win; so I go to standard with the expectation that I’d lose there too for a while but eventually the MMR may drop so some of the games may start getting easier.

But I keep getting netdeck after netdeck after netdeck in standard even after various losses; I wonder if the MMR has a high cap that doesn’t drop unless the month resets; it’s probably not true though and I just won a lot in standard for that to drop with only like ~10 losses.