BUG: Break reference from grouping level to MI
Closes https://github.com/pandas-dev/pandas/issues/31068
> is this just a regression in master? (so no note needed).

Yes, this is just a regression from 0.25.x > > is this just a regression in master? (so no note needed).
> 
> Yes, this is just a regression from 0.25.x

your comments are conflicting, if this is from 0.25.x then we need a note Sorry, I wasn't clear. by "from 0.25.x" I meant "after". This is fixing a regression that's only present on master, not 0.25.x. thanks @TomAugspurger 