Dude is out of his gourd if he believes mechanics are making 6 figures without doing crazy overtime. Just because a job posting is advertised up to 6 figures doesn't mean they will actually offer you such a wage. I live in Michigan and am from a family of mechanics and 95% of mechanics never break $100K ever.
He is also extremely ignorant if he thinks it takes 5 years to learn how to take an engine out of a vehicle, people get PhDs in 5 years, and I could teach someone to remove and replace a certain vehicle's motor in a few days at worst including most of the tips and tricks when things don't go smoothly, after a year I would expect them to be able to take out any motor from any vehicle without guidance. Taking a motor out of a vehicle is one of the easier parts of a mechanic's job, the hard part is being able to diagnose problems without tearing the entire motor out before you know it needs to, or figuring out how to fix a problem without tearing apart every nut and bolt on the car per the official repair, especially as a dealership mechanic where you only get paid a set minimum price for each job no matter how long it takes you in reality. Sure a brand new vehicle might have bolts that spin off in 10 seconds, but the crusty rusted out car from Michigan salted roads might require torches to remove it or time to extract a broken bolt, or drilling and tapping and helicoiling a stripped hole. Even if the hourly labor was free, the parts that either MUST be replaced once bolts are pulled and seals broken, or will inevitably be broken in the process of removal no matter how careful you are, still cost money.