If the female is not yet spayed, there is no benefit (only risk) in allowing them to interact before she is spayed. By risk, I'm not referring to pregnancy but to them sabotaging their chances of a bond in the future.
With her hormones still intact, their behavior will be affected (hers by her hormones, and his behavior can also be affected by her hormones). So if they are allowed together now, they may fight, which could destroy their chances of bonding after she is spayed. But even if they get along, it won't make any headway toward their bond because she will return from the vet... 1. needing to be kept separate while she heals (separation breaks bonds) and, 2. her scent and behavior will have changed making him react to her as a different rabbit.