I mean when Applejack replies to the CMCs with "yep" and "nope" and Big Mac lets loose on them with a long-winded tirade, that's a reversal gag that works really well because it reads so clearly. It's obvious what they're pulling off, and the timing has elements of surprise and keeps building and gaining steam toward a climax.
This scene, if that's what they were going for, felt a lot more forced. Partially because a)
ranting isn't Pinkie's signature personality trait, it's being fun-loving and effervescent (Pinkie going

is kind of a reversal of our expectations of
her already). And b) having her stand quietly in the background doesn't read as "she's behaving like Fluttershy", but rather like "they forgot to have her do anything in this scene".
It just doesn't come across as clearly as a reversal gag needs to, and—well, they've shown they know how to do one by having done several in the past already.