I believe that the first impulse for the rotation is the back leg drive but soon after that the hips turn on an autopilot and the rear foot usually gets pulled forward as the weight is shifted with the swing. You don’t squish the bug but the back foot releases and slides forward. This is mostly a passive process, the leg is pulled forward by the rear hip.
However I think that one mistake can lead to losing posture and swung plane. You want to maintain that slight tilt over the plate so that you can swing perpendicular to the upper spine ( some tilt the whole spine and some add some side bend so the the lower spine is more upright but the upper spine needs to be tilted).

Now here is the mistake. Many kids bring the back foot around toward the plate with the hip rotation. This causes a balance loss and as a result the player stands up and loses his balance and swing plane.

Here is a demonstration

http://youtu.be/JYdsE6YmNrg
Now the better way is to have the foot pulled forward in a more straight line or actually behind you ( back foot toward shortstop for a right handed batter). This gives you a feel of the rear hip coming forward more in a straight line rather than around ( even though in reality the path still is rotational) and gives some counter balance to the tilt so that you can maintain that posture through the turn.

http://noontimebaseball.com/wp-content/uploads/2014/11/Miggy_fronthigh.gif

It doesn’t have to be that extreme but at least make sure the foot comes forward straight and not to the plate.

For myself I have used the cue slide the back toe to the front heel and it has helped my balance.