Baytril is a wide spectrum antibiotic used for many different types of treatment's in reptiles. I've used it to treat wounds, RI's and even to ward off infection from Belly Rot.
Many vets will start with this as it is merely the first step in a treatment. As for the number of injections it all varies from vet to vet. I've given as many as 10 and as few as 4 before it depends on how bad the RI is and the over all health of the snake. A snake that is relativity healthy will be give Baytril to supplement it's own immune system where as a snake in poor health will be give Baytril piggy backed with something like Fortaz and maybe even an appetite stimulant.
So would I dis-agree with the vets decision nope..