Been there man, had a kid last year tell me climb milling is the only way on our old Bridgeport clone. Ran a 1018 block with a 3/4 end mill and watched the whole thing howl like a banshee, switched to conventional on the finish and it cleaned right up. The textbook stuff doesn't teach you what a machine actually sounds like when it's fighting you. Give it a few months of busted inserts and he'll come around.

Did you ask him why he dumped it?

My buddy Marcus had the same thing happen but with steak. He was a total grill guy, always did the highest flame possible and flipped every 30 seconds because some YouTube chef told him that was the move. His wife finally got him to try the reverse sear thing in the oven first at like 225, then a quick sear at the end. He texted me a picture of the thing and I swear it looked like a restaurant plate, perfect pink all the way through with that crust. He still brings it up at every cookout like he discovered fire. What got me was he wasted a whole summer of Saturdays doing it the hard way before he'd even try something different.