Let me refer you to
a post of mine above.
Which other supposed myths are you referring to, exactly? That the tank wasn’t redesigned when lower engines became available because it would slow down production? That would hardly be a myth: redesigning the basic shape would cause all sorts of delays, not to mention logistical problems that you can do without in the middle of a war. Fact is that there were several designs for improved Shermans, including things like welded turrets, hulls with sloping sides, a lower hull and more, and none of those were put into production.