If "many many men (sic)" are saying different things, some...most, perhaps...have to be wrong. It stands to reason. And those who buy into those "different things" without experience or reason (logic, thought, deliberation) will be wrong as well. If the shoe is built correctly, the heel will sit flat when the last is in the the shoe. If the last is designed correctly, part of its function is to support the foot. The shoe does bear weight in the waist--from the heel height to the treadline (ball of the foot). The shank support is like a bridge from the height of the heel to the ground. As with any bridge made of flexible or weak materials it will sag under load. If, as many high end manufacturers (and some bespoke makers) insist on doing, a wooden shank support is used in a shoe, chances are high that the shoe will begin to break down under the weight of the foot. Maybe even immediately. This is one reason a heel can appear to be high at the breast. If such a heel is left alone, the breast of the heel will push up--to its original position during wear and weight bearing--the way the shoemaker and the last maker (and presumably God) intended. If the heel is "leveled" the breast cannot return to its "lasted" position and it will fail to support the arch of the foot. Do this enough...or enough times...and the shoe is ruined.