Hitting mechanics-back foot

Okay i have a question regarding the back foot of hitters. We’ve all been told to rotate the back foot to get the hips through but i’ve noticed something different about all these big time major league hitters dating back to the babe and mantle. They all seem to rotate their back leg/knee in moving their back foot forward, not so much twisting, to the point where sometimes their foot even comes off the ground. Take a look at these video clips and let me know what you think of this.

http://imageevent.com/siggy/hitting/pro?n=0&z=9&c=4&x=0&m=12&w=0&p=0

So the old “squish the bug” cue is really inappropriate because one keeps their weight on the back foot when they squish the bug whereas the MLB guys shift their weight off the back foot. Correct?

it’s all about balance

Seems to me that only the enormous brutes (bonds, howard, giambi, griffey, etc) keep their weight that far back. The more average-sized people are more balanced.

No ML hitter, when he hits the ball well, actually squishes the bug at the point of contact. In many cases their back toes are completely off the gound.