Your right, should be one single pipe loop with branches off the each radiator. If you pipe in and out of each rad it would be very unbalanced and closing one rad off would cripple the system
I'm not an older boy though, I'm only 31, maybe that is old
If your old I'm past it then as I'm 36 lol. It just seems now you very rarely come across them where as the old boys who are probably nearing retirement would of been installing them.