It is not normal and I would not listen to that vet
(unless of course the dog has an empty stomach). I can tell you that Ellie used to throw up every week or two for no reason and she was free fed, so she could eat whenever. I thought I was gving her a good food (Science Diet) but then we switched to Canidae and then homecookiing and she has only thrown up about three times in eight months
and there is always a reason (doesn't feel good, car sick).