Sort of... It is not just the turning out of the feet, but the combination of that and the bending of one knee inward which facilitates the rotary action of the hips.

For example, if you want to maximize the amount to which you can rotate your right hip back, you would need to make sure that your right foot is turned out, and that your left knee is bent inward of the left toe. If you take a classical ballet "plie" position (bending both knees outward at the same angle as the toes), you will find that the hips stay perfectly neutral. Leave the right knee straight while bending the left knee to the same outward angle as the foot, and your right hip will settle back to a limited degree. But as soon as you roll the left knee inward of the foot, (which causes the foot to roll towards its inside edge), you will free up the right hip to rotate even farther back.

On the Cuban Walk, you will notice that the entire leg rotates outward as the body moves away from it. When the body weight has shifted completely to the front foot and the back toe is fully pointed, the knee and toe are then rotated to the same direction. However, when that same knee bends again, the knee will rotate back in and the foot will remain turned-out. A very common mistake is to allow the foot to rotate back in with the knee, which sacrifices the turnout, and therefore the full effect of hip action, of the next step.

Jonathan

The heels turn it, or more appropriately the toes turn out, to give you a more solid base. Keeping your toes turned out gives you more stability and allows your hips to open more...to get the fullest extent of your action.

Having toes turned out force the use of foot's inside edge, which in turn help the cuban motion. In fact, having toes turn out kind of force the knees to be in and that ease or make the hip movement, thus cuban motion.