i know the same way an electrician, a butcher, plumber, baker knows when someone with no training is pretending to be competent, i know because i was trained in a 5 year apprenticeship starting in the sink. When someone puts that jacket on they should be minimally capable.How do you know that? His technique may be the way his family makes pasta. How do you or anyone else know? Have you worked their line? Have you eaten there?
Not everyone makes things the same way. Just because a person makes things different than you do doesn't mean it's wrong, especially if they get a similar end result.
I don't dice onions in the traditional chef manner, but I DO dice onions in the way a respected chef does because that's the way she learned as a girl in her family's restaurant! And she and I get the same result as the traditional "correct" technique.