You don't need to use the square brackets when making a bulk update request (BUR). Remove them first, then it should work. Otherwise the brackets are going to show up in the actual tags themselves.
Posted under Tags
Edit: but both tags aren't used often, so I'm unsure on how useful an implication would be.
There most definitely will be people tagging alternate hair length thinking it doesn't count as alternate hairstyle, an implication could prevent future troubles
also, these tags aren't used much cuz not many know their existence, for instance hagoromo lala and hoshina hikaru have a lot of posts with their official alternate hairstyle yet not even one of them has the tags.