This vet is recognized in our community as a rabbit and exotics specialist. He is highly regarded and we followed his instructions. In this case following his instructions is the right choice.
2 weeks after the surgery the site is almost entirely healed. I wish I had a picture of it to begin with because looking at it now, it difficult to believe the wound could have been as large as it was.

Why all of this was the right choice in this case.
This is an indoor rabbit, we do not have flies in the house. If there was any chance of flys getting near her wound fly Strike would be a real concern.
A cone on a rabbit to prevent her licking her belly is potential option. BUT it would also disrupt cecotrope eating and that could cause diet and digestion issues. It should only be considered with a full understanding of the issues and a plan to address them.
This rabbit is in the house with excellent litter and hygiene habits, her litter box is in our bedroom so it is emptied well before it gets ripe.
Rabbits heal fast, I had no idea how fast until this episode.
We were able to closely monitor her incision for signs of trouble, if a problem developed it could be addressed at the first sign.
After the stitches were gone, we stopped trying to keep her from licking the area. In the end she kept it very clean, and we never needed to wash it. A scab did not really develop until the end, the incision site just kept shrinking until it became the tiny spot that then scabbed over, in the picture.
If the rabbit had any potential for exposure to flies, or insects. Or if the rabbit tended to have a messy bottom this would not be a good choice, going back to the vet and getting the wound re-closed with staples would be a good idea. Also using a mosquito net to protect her from flies would be good.