When in doubt, ask, "What are you trying to accomplish?" If the player says, "My character is trying to shoot the moon with an arrow," that's a good indication of assumption clash. It may be a good opportunity to add detail or context to the setting or situation. In most cases, you and your players shouldn't have to choose between verisimilitude and fun.
I totally agree there are different kinds of players who want different things out of the game. But apart from some comedy games, assumption clash is pretty much always a bug rather than a feature.
Sure, it may be a clash of assumptions because (for example) the player is confused about the context of the situation. But I think it could be more fundamental than that.
I took the example of shooting the moon right out of the section of the DM that describes the process by which the DM must decide whether an ability check is appropriate in order to point out that, if you don't "believe in auto-fails," then you may arrive at unwanted outcomes such as the one described. Because "auto-fail" is something a DM must decide upon from time to time, at least according to the process of adjudication described in the DMG.
As I see it, what happened here was: DM said a particular option was impossible. Player tried to do that impossible thing. DM then decided it was possible, if uncertain, by allowing an ability check. If, instead DM said something like, "The warrior snickers at your attempt to intimidate him, noting in just a few harsh words that you are badly outnumbered here and any move toward violence would be unwise." This outcome would reinforce the previously established context that the guard isn't letting anyone past who wants to see anyone other than the chieftain. The player could then give up or try something else. That might have resolved the bad outcome described.
It is possible, of course, that the player simply didn't understand that bit of established context in which case we have a clash of assumptions. If, however, there is a "playstyle" at the table wherein any given action can get an ability check ("don't believe in auto-fails"), then we potentially have a situation where "roleplaying can diminish if players feel that their die rolls, rather than their decisions and characterizations, always determine success..." (DMG, page 236). The player doesn't really have to pay attention to the situation at all and try to come up with a good solution to the challenge. All he or she need do is try to get a high bonus to an ability check and then perform that task to deal with the challenge. That sounds like it could be the case here.
Or maybe it's not! Either way, I think the analysis is useful and interesting.