Really? That's really interesting to me.
I've always felt Alucard comes off as really hypermasculine, just not the standard western Arnold/Stallone kinda way, an ikemen or whatever it's called. Kind of like JoJo characters to an extent. At least in official artwork where he's wide as a fridge and has gigantic hands.
I guess his old english deep voice-over also helped.
Well, you have to remember that he is wearing some armor and a cape, which would add bulk to his upper body. His face is drawn to be fairly pretty, due to most vampires in media being pretty, and Japan loves their pretty boys.
Alucard could very easily, in my opinion, crossdress and pass as a woman.
Yes, admittedly he isn't a slim twig like most femboys in Anime/Games but he is not a hulking, Roided out male either, like the JoJo characters or Arnold Schwarzenegger, Ect.
But I see your point. He did have a fairly masculine voice in SOTN, and even the Netflix series was more male but slightly soft as well.