We learned to do valve jobs as well. It's just not realistic in the regular auto world. The first problem is the equipment just isn't available in these shops. It's a replace, replace world. I always preferred to rebuild or fix something and often had to fight to go that direction. I remember when I first moved here and got hired at the local GMC/Pontiac dealer. There was one guy that could rebuild a transmission, one. I was the jack of all trades. I was 22 and ripped the transmission out of a trans am to rebuild it. I later found out that the other techs had a bet on whether the car would ever move again.
Of course it did.
When I think of engine machining it consists of crank turning, boring, line honing, sleeving, decking, cutting valve seats, new guides, etc.
Clearly in this small aspect of the auto world,(Resto-mod)machining and fabrication is very important. Only the high end shops do much machining.
I don't disagree that it's a positive thing to teach new auto technicians. The majority just won't likely ever use it again.