A rule can have open ended adjudication by the DM. It could state in plain english the effect. Let's forget about the actual charm person spell. What if the spell just said "the person has a positive reaction to you in a way similar to that of a friendly acquaintance". Just because a DM could in theory misjudge what a friendly acquaintance means does not make the rule bad.
It makes it vague, and clarity is among a variety of desirable attributes that make for a good rule. And it could very easily lead to the player selecting the spell thinking it does something very different from what it will actually do when he uses it, which is not a nice thing for either the player or the DM when it happens.
Even if you don't want to label such a rule 'bad,' it could certainly be better. For instance, in the way the 5e Charm Person spell shores itself up by referencing the Advantage mechanic.
The Emerikol Fallacy says that the potential to adjudicate a rule poorly does not make the rule a bad one.
I know it /states/ that. But, stating something and giving it a cute label doesn't make it true.
I'm still not convinced. Either you've got a valid construct there, or you're bordering on committing an Oberoni Fallacy, yourself, in constructing it.
One of the sticking points - and there are several - is that 'adjudicate' or 'interpret' can shade into actually changing/overriding the meaning/intent of the rule, much like house-ruling. Taken that far, it's no problem. Changing a rule to a broken form and claiming it was already broken is a clear fallacy.
OTOH (and another sticking point), if the rule is so vague that no two DMs are likely to agree on what it means, then which interpretation is the rule and which the changed rule? At that point, you certainly don't have a good rule (nor even a bad one - it might not be a rule, at all, but a hole in the rules). It would, indeed, be technically incorrect to say that a rule that doesn't exist is 'bad.'
OTOOH, even if you do trot out this 'fallacy' in defense of a bad rule and people buy it, you still haven't proved that it's good, just deflected one instance of it being bad. If you stretch it such that it can be used to deflect any instance of a bad rule being bad, it becomes meaningless, and the use of the fallacy in that mode would be a fallacy, itself, and one very similar to Oberoni.
I as a DM could wrongly believe that climbing is super hard and I could consistently make the DCs way too high. This would not make the skill system a bad set or rules.
If the system gave you reasonable DCs, you'd've gotten a better result from it. A system that delivers a better result is arguably better, no? Of course, you could over-ride the system to get the same poor result, but, /then/ you'd indeed no longer be reflecting the quality of the system, but your qualities as a DM.
Oh, and for the nth time, stop pretending that people who disagree with you "don't understand," it's condescending and rude. You might even want to open yourself to the possibility that you could just plain be wrong about something.