At my tactical limits, my main rotor would have been lower than a Twin Huey's skids at its tactical limits. It's as simple as that: nothing more than an illustration of the differences between those limits.
On the CH136 course, all pilots and observers were trained in underwire drills.
In 444 Squadron, we routinely flew under wires and bridges, in accordance with all applicable flying orders.
Did I ever/would I have flown under something actually 15 feet AGL? Not bloody likely, in peacetime at least.
Don't get so worked up over nothing.