This is true. I seen quite a few instructors with the "Do as I say and not as I do" complex. But many times it’s a "I’ve been there and done it a gazillion times, so I learned from experience". For example I was with a group of students last fall doing their OW course. I probably have 1,000 dives on this particular rock jetty. I know where every beer bottle is on the bottom and what my air consumption is, and can navigate it at night with no compass on this jetty.
The drill for the class was the student would hold the instructors alternate and they’d swim out about 50 yards, then turn around and come back. I tagged along for fun. The instructor asks the students, "How much air you got?" Everybody was about 1,000. I had 300. "You don’t have to go then since you only have 300 if you don’t want to." the instructor said. I replied, "I’ll go. If I get low on air, I’ll surface." Now if I was out on a wreck that I was unfamiliar with, I’d adhere to the "must return with 500 PSI" rule. In this particular scenario, it didn’t matter. I’ve returned to the boat with the needle on zero before. It’s 40 feet. The tank at the state aquarium is deeper than that.
But you were right in your call about your buddy. I’d never leave a buddy who was less experienced than me. I dive the jetty with some of the guys at the dive shop and they don’t care. But they all have a gazillion dives under their belts. They just swim off and do their thing. I had one buddy last year I went with. He got all suited up on the boat ride out. I didn’t because I was busy driving. So when we get to the site he jumps on in and just disappears while I’m getting my crap on. So we both did our solos dive and I surfaced about 45 minutes later and just waited. He finally showed back up after about an hour with a bag full of crab claws. I was starting to get worried because I knew an aluminum 80 lasts me at most 70 minutes at that depth. I was thinking, "How long should I wait before I call the Coast Guard?" LOL