Tendon repair surgery is not uncommon for humans, esp in cases of complete achilles tendon rupture.
If a tendon is completely severed, with no segment of it holding it together, the severed ends will be pulled in opposite directions, which means they nolonger have contact and thus can’t heal. But if there is some part of the tendon that still is intact, or if tendon surgery is at least partially successful, chances are the tendon can heal. Depending on what tendon is torn, there might be other, nearby tendons that can compensate for the loss of the torn tendon. I’m thinking this is why the vet wants to wait and see for a little bit.
Rabbits are notoriously bad at keeping casts on, but in this case fixation is very important. With a broken bone you can sometimes skip putting the leg in a cast, if the bone ends are aligned and stable. Putting a cone on a rabbit isn’t ideal, but there are instances when it is needed.
As Wick says, tripod rabbits tend to do great. Animals have a much bigger part of their brain dedicated to movement and balance than humans have.