It seems that when a man impersonates a woman in fiction or history accounts, he does it for safety or erotic reasons - hiding or gaining entrance to otherwise forbidden place. The example you found does indeed look interesting, and, again movies like Some like it hot immediately come to mind, but strangely this trope isn't that popular in sf, even for comedy purposes.

You are right about patriarchy and possible advantages, but as it seems one of the possibilities of sf and fantasy to create societies with different rules and mores, one can invent the one with other advantages to pretend to be a woman, other that get into a harem. Let's hope we'll read it eventually!