Long hair is a reasonably common fetish, with a good evolutionary justification (if someone has long, healthy hair you can be assured they've been healthy for a while).

It does seem to be commonly fetishized, and at least one major fantasy novelist transparently has such a fetish based on his writing which may have also made it more common among geeks. But the health explanation seems like a bit of a just-so story. Plausible, but very hard to test. And we don't really have any evidence that this trait is genetic. Meanwhile, it is just as plausible that the fetishization occurs the same way many objects, clothings or the like become fetishized even when those things did not exist in our ancestral environment. No need to posit multiple mechanisms.