No, it is not true that they CAN'T file a report. They may or may not bother, but they most certainly CAN.

The first day you can move out and have it be absolutely certain that no one can drag you back is your 18th birthday. As long as you are even one minute under 18, you live where your mother says you live. Law enforcement may or may not participate in bringing you back home but that will be by choice, not because they are prevented by law. And your mother can drag you home whether they are willing to do so or not.