A couple times I've had people head towards me to help while I was backing in, but they would stop when I just put it in place - decades of pulling similar sized landscaping trailers.
One time when we pulled in at night we had 3 guys "help" me back in - they were camping together, so thought it would be great to all help. It was a minor nightmare of yelling back and forth, conflicting directions, etc. After I got backed in and they left... I pulled back out and re-backed in, my trailer had ended up on the wrong side of the site (the camper door opened into the neighbor's fire pit...).
I've never really "gotcha'd" anyone. Probably the reverse, though... people have come up to compliment my truck (big red crewcab, with a big red cap on the back), and then I mention that it is 2 wheel drive and they sort of look crosseyed at me with sort of a "Oh, you poor thing!" look.