Uhm...I feel like this story could have worked without the medieval era background, could have modernized and kept royal ranks and stuff, making some parts of the common sense work in the setting better, but that is just my personal opinion, it works even like this, I just feel that it seems this way for the popularity of medieval fantasies in the last years and could have done without.
For who is confused about why MC is confused about discovering she is a woman when thinking "she" just before, in japanese there are gender neutral ways to refer to someone, so when the translator had him using female pronouns it was a small mistake, the MC most likely used a male or neutral one in the raws, is no biggie.
Is a gimmick used every once in a while, some TL have a explanation, some don't, possibly counting on readers experience, but it can still get some new ones or event old manga fans that simply never read a story with that trick.