Do you know if the vet that you went to is rabbit savvy? If so, maybe they have reasons to believe that they may be a obstruction in your bun’s tummy. If there is a blockage, then force feeding could be very harmful to the bun.
When I took my bun from GI statis to the emergency vet at night, they put him on the same stuff that you mentioned in the post and referred him to a vet savvy vet. The vet savvy vet was the one said antibiotics is not required (in my case) and changed the dose of the medications. Then he said that it may be from a molar spur but unless the bun is put under anesthetic he cannot tell for sure. The vet explained that he was reluctant to do it unnecessarily and putting him under more stress.
Sorry to be going off the tangent here, but my point is if your vet is rabbit savvy, then he might have had a good reason and should have explained to you why he is doing so. If he is not, then maybe he is just unsure (i’ve called up a vet practice and was told that their vet isn’t comfortable handing rabbits).
Hope Basil will be much better – keep us updated!