This is not my experience. I've played with very "Mother may I" GMs - with AD&D 2nd ed as the system - who had consistent visions of their world.
As I think
@hawkeyefan posted not far upthread, and also
@Pedantic, the issue was not the consistent or inconsistent vision of the world, but the way the GM exercised authority over action resolution.
Players getting to declare actions for their PC is the minimum thing that needs to happen at a table for it to count as a RPG. So if we take as a premise of discussion that some RPGing might count as "Mother may I", then we can't confine the label to cases that wouldn't count as RPGing at all.
This is why I have been disagreeing with
@FrogReaver (in particular) and some other posters also that the players ought to have no concern about what follows from their declared actions. The point of playing a RPG isn't just to describe the bodily motions and mental states of one's PC. It's to impact the shared fiction, through declaring actions that have consequences. And "Mother may I", used in the context of RPGing, is a label for certain ways of "gating" or arbitrarily determining those consequences, that are made possible by (though not necessarily entailed by) a particular sort of authority structure.
This is also why I regard pointing to the 5e core play loop as incomplete. I think it's obvious that the play loop is to be supplemented by certain principles, and that some of those principles will reduce the likelihood of "Mother may I" moments in play. (This is the bit of the discussion involving
@Ovi and
@Maxperson about trying not to say "no" and the like.)
My question, reading this story, is
How did the GM decide the bandits' reactions to these people they met with a friendly Bard as their herald (or leader - it's not clear)? We've got an action declaration - an attempt to befriend these men. The GM decides that the men are
not befriended, that they
mislead, and that they then
backstab. How was that done?
Inferring from your (admittedly brief) presentation of it, it seems that the resolution method was simple GM fiat. The Gm seems to have taken for granted that the situation is a puzzle, with the fixed parameters that accompany a puzzle: these NPCs
are hostile, they
will attack the PCs regardless of how the PCs greet them, and the players have to figure this out by correlating (i) observations of the wounded, tired state of the NPCs with (ii) stories of bandits.
I think puzzle-type play, in a context where the GM is also rather casual about how they dispense information, and where expectations/conventions aren't clearly established, is a recipe for "Mother may I" of the highest order!
An alternative way to run the bandit scenario would involve the GM rolling for a reaction on the part of the bandits in response to the Bard's friendly greeting, with the possibility that the bandits don't attack the PCs because they like them (presumably even bandits have friends) and try to get them to realise that its the PCs' employers who are in the wrong (maybe the bandits are really Robin Hood-types). Or Princess Bride-style, the PCs make such a good impression that the bandit leader openly says "I hate to have to take you prisoner and ransom you - maybe we can duel over it!" Or whatever. There are many, many ways the amusing premise of this situation could play out which don't involve treating it as a puzzle and which might not have caused the same degree of upset to the players.
I think upthread I mentioned the difference between The Green Knight and Agon - both involve making inferences about what should be done (honour vs dishonour in the first; the will of the gods in the second), but The Green Knight is puzzle-solving (because the GM has established an answer as part of scenario design) and Agon is not (because the players interpret the signs of the gods, and the system has other ways for "punishing" them if they act contrary to their interpretation).
If the players don't even know whether they're playing Green Knight-style or Agon-style (or maybe some further, different style) that could be pretty frustrating!