Listening to some of the brain rotten takes by trannies online about "hidden trans allegory" in Fate makes me think of an earlier proto-form of the same horseshit..."feminist readings" of classic literature.
One case in point, I believe it was Pride & Prejudice where two female characters were declared to be "secretly lesbian" because they would always accompany each other when they left the house... ignoring the reality that 1800s upper class women would do this for social etiquette reasons (ie. one of them going out alone might fuel gossip and scandal about secret trysts or affairs, to say nothing of the danger of a young, wealthy woman going out alone).
Point is, when you divorce a story from its historical, authorial, or any other context and then cherry pick details to fit the conclusion you want to be true, you can "interpret" anything to mean anything...its a pointless fart sniffing exercise.
tl;dr: Saber from Fate isn't a trans allegory of anything, they just didn't want a hairy bearded old man standing across the male protagonist, duh.