That might be the case in restaurants that can afford to pay a manager to sit in an office while the rest of his staff works, but I guarantee you I squeezed every last possible ounce of work out of myself so that I could run down my labor cost by NOT having people scheduled doing work I could be doing. It's not easy to do at a QSR in a college town with super competitive (read: low) menu prices.
I was essentially working as hard or harder than everyone else in the store at any given time. I don't think a manager that does as you describe can effectively manage a good operation because they'll just be looked down upon by the rest of their staff as you're implying, and that wasn't me.
Very much doubt I shortened my life by 10 years and I now work behind a desk at a major game company that takes very good care of my health, nutrition, and fitness. Yes people have different thresholds but never being willing to push yourself isn't good either, it's a great way to remain perfectly mediocre.
Different strokes for different folks.
