"I wonder if this means that a load of chilled # 8 shot dropped by a MEC 1 oz bar would weigh more than a load of magnum 8s dropped by the same bar?"
Yes, it does mean that, but you're OK since the shot bushings are generally set up for chilled shot.
You'll get about 0.97 or 0.98 ounces or so when you use magnum shot with a 1 ounce shot bushing, but you'll get the same number of pellets.
"would it be safe to conclude that a shell using chilled shot would recoil MORE than a shell loaded with magnum shot, since the weight of the shot is a factor in computing recoil?"
Physics tells us it must, but your shoulder won't be able to tell the difference. Like I said, 6% antimony magnum shot is about 0.97% the weight of pure lead. Chilled lead does have some antimony (less than 3% if I recall correctly), just not as much as magnum. The difference is inconsequential.
In my opinion (timb99's mind only) chilled versus magnum probably doesn't make a hill of beans worth of difference at 16 yards. I use whatever is available and cheap for my singles reloads.
Though for my own peace of mind, I use Remington magnum shot for my handicap loads.