This is very hard spoiler. Perhaps ? Spoiler she's a futa !? When and where she's a confirmed futa !?
I don't play FGO, because FGO is secretly a very large harem (all heroic spirits) anime disguised as game.
ANYONE CAN BE A FUTA!!! ANYONE CAN BE A DOUBLE FUTA IN DOUJINSHILAND!!!! But seriously, @reagents 11 , unless the source, Typemoon(?) or the company who owns FGO franchise says Vinci chan is a futa, she is otherwise a schrodinger Futa, like all the rest of the female casts.
Spoiler: From fate wiki, make your own conclusion: While a male normally, da Vinci says that the Mona Lisa represented the ideal beauty she pursued during her life, so she feels nothing wrong in having become that beauty itself.
Why are you under the assumption that all heroic spirits I mentioned were girls? *Aizen music* The female or male players could have their own harem of male or female (or both) servants, even those non-binary gender fluid physical alterations.
Doujin then sure, but official then no ^ While if you get it from here, then it's Gender Bender. (random but I just started FGO, so anyone want to add friend with me?)
Lt.Yurisaki(NA server) UID 495,211,914 F2P Account lvl80 Altera NP1 lvl80 Merlin NP2 too lazy to grind mats, add if you want