There's no ambiguity. There is no subjective definition. No hairstyles exist that do not include a length. The length of your hair is part of the hairstyle. It is stupid to argue, on that we agree.
You cannot have a mullet with long hair in the front and shorter hair in the back, because that's not the hair lengths of a mullet. You cannot have a mohawk with long hair on the sides and shorter on top. You cannot have a long, curly crew cut. You cannot have pigtails with a completely shaved head.
Hairstyles always, inexorably require hair length definitions. Anything else is a disingenuous argument, an attempt at semantic skulduggery. It is a lie to say that hairstyles don't include length.
There is no technicality, there is no advantage, there is only racism and injustice. This judge is a fraud, the school superintendent is a fascist bigot, and this ruling is a crime against humanity.