One thing you will see in almost all high level swings is at contact there is little and sometimes no weight on the back foot (it really does not look different). In fact a lot of hitters right at contact actually are not even it contact with the ground. The reason being is they have transferred all that energy into the swing. Swings are built from the ground up I love your advice to learn to coil first but if you don't uncoil properly (release the hip and put pressure on your rear instep) and simply spin around and leave a lot or weight on your back foot the perfect "coil" did not do you any good.
The "ground up" concept is one to be careful with. It is often interpreted as the swing being initiated by a pushing action with the rear foot. There are forces against the ground at the rear foot, and the location and direction of those forces are important, but much of the action at the rear foot is a result of things happening above it.