I'd get a second opinion. I'm not ultra keen on preventative surgeries when there's a good chance the dog will have no problems arising from a conformational or structural defect. Many dogs live perfectly normal lives with an underbite.
That said, small breeds + a smooshed in face can create a disaster when it comes to teeth...so your vet isn't necessarily a crackpot or just out to get your money. Mother nature never intended to have all those teeth fit into a small, flat space...so it's not uncommon for pugs or frenchies or other similar sized brachycephalics to need teeth pulled in order to have a more normal mouth. Another example of how our desire for looks overrides what is best for dogs.
That said, small breeds + a smooshed in face can create a disaster when it comes to teeth...so your vet isn't necessarily a crackpot or just out to get your money. Mother nature never intended to have all those teeth fit into a small, flat space...so it's not uncommon for pugs or frenchies or other similar sized brachycephalics to need teeth pulled in order to have a more normal mouth. Another example of how our desire for looks overrides what is best for dogs.