Then why can't we have something non-magical with its own set of rules in and out of game?
Like the exact ability that's being discussed.
What about doing some pelvic thrusts and eating an insect makes subverting the idea that the DM gets to decide how NPCs react suddenly okay when it 'broke the game' perviously?
Okay, let me try to explain it:
First I will differentiate some vocabulary:
Ingame fiction is the game inside the world how the characters would see it as ifnthey would really exist.
At the table is the game experience fornthe players.
In D&D at the table, the players decide how their characters act. The DM decides how the rest acts.
That is mirrored by the ingame fiction.
No charavter can compell a NPC to do anything specific with mundane means. They can influence them, by lying to them, persuade them, intimidate them, bribe them and so on, but what exactly the NPC is doing the character can't decide the same way you and I can't controll what any other person in this real world is doing.
Everybody has their own free will and everybody can only try to influence the perception of another being with mundane things like talking to them. The NPCs ingame have a free will. At the table they have the illusion of free will (because yes, they are controlled by the DM).
In D&D Magic can directly influence the mind and compell somebody to do something specific. But it doesn't contradict the mundane reality. Because what Magic does is taking away the free will of a character by magical means. Using magic to controll someone is the equivalent of putting somebody in chains and moving them like a puppet.
It works on the table as a rule and it works in the Ingame fiction of D&D.
For example: Moving a character by magic is the same as grabbing them and moving him by force.
If you would have now mundane non forceful (physical) abilities that allow you to move somebody in the exact same way you did with magic or by grabbing then just by talking to them, you break the Ingame logic.
You take away the "free will" of the NPCs. Suddenly just by talking NPCs do exactly what you want.
On the table that would break immersion, because now the DM has to alter reality in the ingame fiction to accommodate the player action.
It lays bare that the NPC is just a game mechanic at the wims of the players NPC controlling ability.
A Spellnor magical effect doesn't do that, because it is not breaking the ingamr world, because it is part of the ingame world.
It s like in Men in Tights when the stop the Movie and get out the Script. It interrupts the fiction.
Of course you could build a game where you have players controlling the narrative. But that for me is like having 6 directors to direct one movie, not an immerwive Rollplaying experience. In comparison D&D is directed by the DM who's job it is to hold up the illusion of a consistent world.