but maybe making Poe (and the audience) feel like something is off about Holdo is the point
The first time I saw it, I totally thought she was a FO spy.
That makes total sense to me, by Lucas’ original Imperial = unnatural, Rebel = natural rule. I can see someone wanting to change it on that basis, to avoid that confusion. For me I can also comfortably assume that the resistance wouldn’t care about hair colour since in the absence of any evidence to the contrary that seems like a sensible default. But I’m the one who’s very confused about this whole thing so I’m probably not the best judge here!