Virginity was never about sexual integrity but youth. Child sexual assault was rampant thoughout the classical and middle ages. Blood from a sacrifice of any child under majority (fourteen or before first period) would qualify.

Mary and Joseph were totally banging.

That said, most kids were so fucked by life that it was a major deal when one did age up. Despite the Church wanting to execute women for premarital proclivities, the labor shortage was no one else was into it (until you get to high-ranking aristocracy, and even then, only for the hautiest).