I’m 100% in favor of VE/BE sharing hairstyles, more so given how good the VE hairstyles and color fit the undead elf fantasy.
But I kinda get the argument why they would want to keep hairstyles separate in terms of aesthetic identity and styling really is one of those things is culture dependent.
But on that case, why not make them share hairstyles with members of their own race? BE could swap with Nightborne, and Void Elves could swap with either Humans or Night elves.
I think Humans makes more sense lorewise since VE seem to hang out mostly on Stormwind outside Telogrus, so that would be their major influence. Kinda wish they had gone for a stronger connection between VE and Kul tirans in Stormsong Valley, so then they could share hairstyles.