Please, it’s not about guaranteeing blood. It’s giving Muslim men their fill of female pain for the day.
Although many times the pain of a woman’s first intercourse is actually not caused by the hymen but by muscle clenching/spasm, I am betting that a surgically restored hymen is less stretched, flexible and worn down than that of a typical 20-something woman (who even if she is a virgin, would likely have engaged in many athletic activities that stretched if not torn the hymen making it a non-issue for first intercourse - which is one of the major reasons why many women do not bleed). Thus the woman will be in pain, thus the Muslim male is happy.
I'm guessing that the smarter Muslim women (but those who still aren't smart enough to run away from their sick, Neanderthal families and marry a proper, upstanding infidel) will have a small vial of cow or sheep's blood that they got from a sympathetic butcher in their overnight bag on their wedding night. A quick dash to the restroom after 'the deed' and voila! The 'evidence' of her virginity will be made clear.