Our first vet told me to do the same to my pup, despite the fact that he was perfectly behaved during the examination, shots, nail clipping, and bordetella vacc poured down his nose.
After enduring all of that like a trooper, the vet forced my pup onto his back and grabbed his snout. She instructed me to do the same to him every day to let him know who is boss.
We have a different vet now.