I would disagree that it is a good descriptor. I think it describes a feeling of frustration that arises when the GM doesn't let you do anything except the one thing they had planned, or the one thing they think is acceptable in the moment (or the handful of things). So using it as a descriptor would be bad in my view because it automatically encourages a style of play where the GM isn't open minded, fair and welding their power responsibly. If you say "This style is mother may I", then you are going to have GMs leaning into that aspect of it, rather than facilitating play in an open and interesting way. In my mind, a mother may I GM is someone who says no to most things the players propose. And there is also an implication in the name that the GM derives pleasure from denying players whatever it is they were seeking to do.
I don't use it like that and I don't think that is a particularly good use of it.
Its about (a) the process of play, (b) how authority over content introduction orbits around that process, and (c) how a + b inform the cognitive state of the participants whenever they're orienting themselves to a situation > navigating their decision-space > declaring an action.
When one participant has absolute veto over every single thing (or nearly every single thing) + when that same party has a deep role in mediation of action resolution AND determining when a scene has met its end...
Well, that creates that (c) above where the player is thinking as follows during the loop of orient > navigate > declare:
Orienting to Scenario: "What is the GM's conception of this situation they've laid out before us...how can I tease that out (via questions and proposing declared actions)?"
Navigating Decision-Space: "What actions will the GM allow me to perform and what actions will they veto based on their conception of my PC and the scenario in question" > winnowed down to that subset of feasible actions > "What actions will the GM give me a better vs worse risk profile and better vs worse odds of success and (perhaps) what actions will the GM reward me for threading the thematic needle?" >
Action Declaration: Winnowed down further to the desirable subset that subsumes risk profile + odds + rewards for thematic needle threading (if any) >
"Which of these remaining actions is most interesting to me (if any...if not go backwards)? > Choose action.
Only at the very end in Action Declaration (that italicized bit) does your cognitive loop pass over something that is entirely your own. And you may not even get to that stage because the rest of your cognitive loop may converge on a subset (perhaps even just one) choice that doesn't include "which of these remaining actions is most interesting to me?"
So its the GM's conception of setting/mythology/backstory/causality/genre tropes that ultimately (i) introduces all setting/situation content into the imagined space, (ii) forbids content that might be introduced into the imagined space, (iii) vets pending content to be introduced into the imagined space, (iv) dictates/mediates resolution of conflicting interests, and (v) dictates and winnows the players' orienting to the situation and navigation of their decision-tree. Only at the very end of all of that does a player have something that they have complete autonomy over ("is this interesting?") and that subset of their decision-tree may not "hit."
To me, that looks like the phenomena of MMI at play.