Unfortunately, this kind of unprofessional "professional" installer is a huge problem these days and it's not limited to the hearth industry. It's rampant across pretty much all trades. My theory is all the money is flowing to big business like cable, wireless, loans, banking credit cards, phone providers, big construction, law firms, Wall Street and equities, CEO's and management, etc. and there's not much left for the working guy. So you get inexperienced youngsters or adults forced into a trade they have no background in. And it often doesn't pay enough to really live on because people need to buy insurance, healthcare, education, etc. Even some people who have been in the hearth industry for years are not that good because, for whatever reason, they never developed good critical thinking skills or just don't care.
Why don't you buy the stove for self-pick-up and install it yourself. That's what I did and I'm confident I have a better install than if one of the local dealers sent one of their "professionals" out.