I've challenged the overfed bull thing for many years.
I remember taking bulls to Calgary and getting whipped because they were just in good flesh instead of butterball flesh.
Funniest thing was one rancher who took a chance one year and when I talked with him the next year he said that bull was really easy doing. He fed him 5 pounds of oats over the winter and he got plum fat.
Of all the buyers I have had wander the pens, none look at the smallest bulls first. Even one guy from Oregon that was specifically looking for the smaller type bulls went to the biggest bull in the pen and wanted him.
Very few real cattlemen own cattle.