The reason you are instructed to pierce the film instead of peeling is obvious and for a purpose.
If the contents of the meal shift before it is completely frozen the liquid part could collect on one side of the packaging.
When heated in a microwave concentrated liquid could start to boil. If it has congregated at the edge that has been peeled it could boil and expand outside the package, into the microwave. Hence the vile community microwave at work places, created by people that don't understand common logic and reason.
If pierced on the top of the film your microwave will probably be spared.
This isn't rocket science people.