N1 Vibes:
That low-energy/high-energy distinction is one I've never encountered. In fact, I know of a military engine that had some record of "chucking" blades through the case, and in order to achieve a civil TC, some added protection (external shield) was required.
In that case the FAA was having no part of a low-energy/high-energy distinction. A case penetration is a case penetration.