It doesn’t, because unlike in the example of the player saying their character flies across the room (something the general “roleplaying rule” says they can try, but they have no means of succeeding at unless they have a fly speed), the rules for the charmed condition contain a specific exception to the more general “roleplaying rule” - they say the character can’t attack the charmer. Whether a DM decides that they can’t attack because they can’t even try, or they can try but won’t be successful, seems like splitting hairs to me. Either way, the charmed character can’t attack the charmer, because a specific rule says so.
I realise that these arguments are put forward, not from bad faith, but from prior commitments. Game mechanics intrude on roleplaying. They do so in many ways. Sometimes preventing the player from deciding to do a certain thing (a charmed player-character
can't decide to attack). Sometimes deciding what they think (a player-character deceived by an NPC disguise will given facts in mind that are contrary to the truth).
On exceptions to general. The argument you put to my reading amounts to lack of narrow enough specification to satisfy you as constituting exceptions. You hold there is a general rule - roleplay - which is not a rule but a definition in context. Even taken as a rule, social interaction skills can be used - possibly should only be used - as game mechanics in perfectly well specified ways. There really is no lack of specificity in how to use them. And there need be no lack of specificity in the outcome of their use. When used in such ways, they will satisfy the conditions judged satisfactory for the use of other game mechanics. (And this is given that there was any issue with their specificity in the first place, which I do not concede.)
On lack of uncertainty. This is a simple case of cart-before-the-horse. A DM not only may, but
must, decide what is uncertain. They should also consider other factors, like stakes. It is up to the DM in
every case to decide what is uncertain and where the stakes are high enough to matter. There are no carve outs for social interactions in the printed rules. You may believe that social interaction is never uncertain, but that is only because of your prior commitments on the matter. It is normal that DMs will differ on when they will and will not call for checks. The best claim to higher ground belongs to the many lines on the DM's remit, and not to a few words that are about how to roleplay.
I understand that you are unable to see it that way: perhaps that is as far as we can get.