I was asked recently if it was important to keep the left heel on the ground during the backswing. Well, to be honest _ not really.
Lifting up the left heel allows you to make a full turn. Ben Hogan never worried about this as it either came up or it didn't, depending on the swing he was making.
Personally, I think it's just a natural 'individual' style that you will adopt. Keeping the left heel flat on the ground throughout the backswing will shorten the backswing, especially as we get older.