That's just a badly designed monster or badly designed adventure pacing, take your pick. The fun of an encounter shouldn't rely on the party having specific resources.
We have the fiction. This is an almagam informed by:
- real life (human behavior, politics, etc. which we can't agree upon and constantly have debates and even wars over)
- history (knights, castles, etc. and all the arguments about anachronisms, longswords vs katanas, etc.)
- fantasy literature (dragons, magic, none of the which are exactly the same according to any one author)
- D&D fiction (rust monsters and other D&D originals)
- other genre laws (Hollywood action movie tropes and cliches, not exactly consistent)
The sum of all that incoherence is what the in-game characters experience to be true.
But then we have extraneous interests that want to clarify the truth of the fiction:
- adventure format (cliches such as tons of dungeon delves because we don't have time, money and/or inclination to think of more interesting stories)
- game mechanics (surviving 200" jumps, oozes being knocked prone, powers that are effective 1/day, etc.)
- what the DM says
- what the players say
Now on top of that, we also have:
- adventure pacing (narrative that is structured to optimize player experience of the game mechanics, which has arguably changed over editions)
So where do you draw the line? Where's the baseline? Where do you separate what you want to be fictionally true vs what isn't or shouldn't necessarily be true?
Because if you accept that ALL of the above is part of the reality that IS true in D&D fiction, then there cannot be any disassociation.
If you say 1/day mechanism is not disassociated from the fiction, because in the fiction that power is only used 1/day, then it's a closed circle.
There's nothing to argue about.
Conversely, I think I draw my baseline somewhere between points 4 and 5. Which is not to say that anything is set in stone, I often rethink a fictional construct, but that's the general vicinity. So the adventure format, game mechanics, adventure pacing, even DM/player input, may or may not support my vision of what the fiction could/should be. You know how some people say, if you don't like the rules, change them? That's where my head is at. That's how I can see disassociation between mechanics and my baseline for the fiction.
Did I argue that correctly? Or am I belaboring the obvious?