Yit,
It’s not at all dochuk to say that some parts are not era subjective. That seems to be the opinion of the Rashb’a and Ramba’m l’gabay sa’ar beis hashechi, and although the R’ma didn’t pasken that way, and even if we go with R’ A.E. l’gabay mirrors, that doesn’t mean the yesod is wrong. Why broaden the machlokes to make it so yesodosdik? I think my diyuk in R’Moshe is a good one, that dying hair is b’etzem.