It's the only pokemon in little cup that has Drought AFAIK. All they'd have to do is say "no drought!" and that's it. Not very complicated.
Technically they do ban abilities like snow cloak with the evasion clause, but for some reason if it doesn't have to do with a particular clause they just ban Pokemon with broken dreamworld abilities. If you don't like it not much you can do here, you need to yell at them.
"How ridiculous and how strange to be surprised at anything which happens in life!"
Because if there's no reason not to do that, then there's no reason not to retier everything that has a substandard ability, which would require a lot of work to fix while enduring a lot of outcry until it gets fixed. All that because someone wants to use Vulpix.
See, on one hand, when a Smogon rule changes, the whole community will comment/praise/criticise it. But on the other hand, quite a few people know Smogon is just a community and there's no reason to deviate from them if you have a good reason to do so, like in this case. And the folks at Smogon know all that.
So basically, they can't be arsed to work on something so big that will please very few people when those people can, for the most part, fix that problem themselves with some good old fashioned communication!