how do national parks measure the length of a 5th wheel?

A question.
Who here has *personally* , that is no hearsay, not a conversation overheard in the barbershop, but personally had someone from the campground break out a tape measure and measure your rig.

In over 35 years of camping I have never had that happen nor have I ever had someone tell me it really happened to them.

Urban legend me thinks.

It's on my list of stuff to worry about but I'm afraid it's in last place.