A friend (not a foodie) asked my help in cooking "microwave-ready' sweet potatoes. Never having seen these, I peeled off the wrapping, pierced them, and nuked them conventionally. Today, he called from the market, and told me the potatoes should have been left wrapped, and not pierced. Seems unsafe to 1. leave a tight plastic-like wrapper on while cooking, and 2. not pierce to allow steam to escape. Cannot find any online info. What is the story with this product? Why is it even necessary?