In the Hearths Warming special, wasn't it kind of implied that her braids were a fairly significant moment for her? Her braids always seemed tied into her heritage to me.
They just ignored what they built up for the character to put as many makeover clichés in as possible. I was also not exactly happy with the "ewww yak food is disgusting!!!" joke and again the reminder that yaks have horrible hygiene to a point ponies have to wear hazmat suits to bathe her.
It made me feel bad for Yona, she is just a cute kid.
It wouldn't bother me that much if the yaks weren't supposed to be the pony world's equivalent to Pakistan (or generally any eastern mountain folk that use yaks for milk and meat). Like Al-1701 said, the yaks are like the Carbombyans from Transformers. It looks like they did not learn anything from that (they lost iconic voice actor Casey Kasem over these episodes).
Just do not make allusions to real world places and people if you really want to do these "ewww gross" jokes. It could be so easy.
But like I already mentioned, this show has been doing that from the start. Zecora, the buffalo herd and even donkeys. In an early season Rarity was making comments about how ugly mules are even tho donkeys live just like ponies. A mule is when a pony and a donkey have offspring. Classy. And that came from my favorite pony who is supposed to be generous
These writers will never handle these issues with grace so they should have never made different species into different people.
They already did that with the ponies, so there was no need to have more "others".