PSA on MMR inflation if you haven't played since beginning of TWW (1600MMR -> 2000MMR in Shuffle)

I was on vacation when TWW released, so I played WoW on my Druid at the beginning of the seasons. After about 4 or so weeks of Solo Shuffle and Blitz, I hit about 1570CR in Shuffle with about ~1600 MMR and 1670 in Blitz with about 2000 MMR.

I came back to work and got kind of bored of WoW and stopped playing.

Last weekend, I logged on for the first time and queued shuffle on my Feral, and noticed that suddenly I was at 2000MMR from the 1600 that I was months ago. Had to remember how to play again and what my defensives were, and ended up going 2/4.

Today I went from 1570 to 1820CR in about two hours by going 3/3 + a few 4/2s, because my MMR was randomly inflated to 2000 without me playing.

Is this how rating inflation usually works? It's just injected to everyone?