People already complain about abrupt endings in pony, don't they?
Back on the 11-minute vs 22-minute thing, though - I think part of the reason is that MLP is, I guess, just a bit smoother, to me. I mean, I think of 11-minute shows, like Spongebob, or Adventure Time, or Dexter's Lab; and yeah, they can be hilarious or emotional, but it doesn't feel natural the same way that MLP does. On those shows, the characters feel more like vehicles for comedy, or drama, or morals, than actual people, and it comes across as a bit artificial - not in a bad way, mind you.
With MLP, it wants 22 minutes because it's supposed to feel like a very organic experience, and it needs as many seconds as it can get. Like, I think of Pinkie Pride - half that episode is in song - and it really pushes that 22 minutes to the fullest; it makes use of lots of big shots to show the sheer scale of the parties, it has long songs to capture as much energy as possible from Pinkie and Cheese, and not a single moment goes by that doesn't feel meaningful. Having a longer time lets the show really breathe and gives room for all the fluff to make it feel less like a carefully constructed TV show and more like a snapshot into the lives of a small circle of friends.
I dunno, I'm just kinda wordsing and maybe everything I've just said is BS. Still, an 11-minute episode is certainly possible, and if you really do write one, I'd seriously love to see it - after all, I do support both art in any form and diminutive equines - but for now, I don't think the showrunners would do that, because it seems like a pretty huge change in the feel of the show.