I've had a DM who really liked the swap. I have had two others that never swap.
I like the thought behind the swap. It gives it a sense of realism. However, I dislike what it does to the character creation process.
(Not directed at you Oofta, but in general) The character creation process houses a limited number of shiny things for players. One of those things is a skill proficiency. So you have a player that really want great sleight of hand. They spent their resources developing it. Now all of a sudden the DM says, "Well, it's sleight of hand to sneak inside her purse while you are dancing with her, but you need to use charisma instead of dex." Now, suddenly, something this player might have been great at (because they chose sleight of hand because of their high dex) is now just, meh.
Seems a bit unfair, and in truth, it slows the game down. Even with experienced players.
The DM in the example is going about the process backwards. They should
first determine the appropriate ability, and
then determine the appropriate skill. And the appropriate ability is informed by the action the character described. Sure, combining skill at Sleight of Hand with Charisma
might make sense for an attempt to acquire something from an NPC’s purse by slipping your hand in while they’re distracted by dancing. But only if
both Charisma and Sleight of hand are involved. Charisma by itself doesn’t seem appropriate for the task, and so I don’t believe it would be the most appropriate ability for the DM to call for a check with.
The Using Ability Scores section says that “Charisma measures your ability to interact effectively with others. It includes such factors as confidence and eloquence, and it can represent a charming or commanding personality.” To me, that doesn’t sound like it’s the most fitting ability with which to determine whether a character succeeds in the goal of getting an object from another character’s purse by the approach of slipping their hand in while they’re dancing. Like, maybe the confidence part might be helpful? But really the primary thing being tested is how quickly and subtly they can get their hand in and back out. Since “a Dexterity check can model any attempt to move nimbly, quickly, or quietly, or to keep from falling on tricky footing,” it seems like the most appropriate ability to check.
In my view, only after the appropriate ability has been determined should it be considered if a proficiency is applicable. So, would Sleight of Hand be appropriate to add to a Dexterity check to steal something from your dance partner’s purse? Absolutely! Might Performance also be applicable? Performance “...determines how well you can delight an audience with music, dance, acting, storytelling, or some other form of entertainment,” so it seems reasonable to me that the character might be able to distract the mark with their dancing.
If you do it this way, it actually gives the players
more opportunities to apply proficiencies they’ve spent character building resources on, because you’re not limited to certain proficiencies only applying to checks with certain abilities.