What's the purpose of this for a truck camper?

If they are different sizes, then one's a Class V connector (2 5/8) and the other is Class III (2").

If they're the same, then like the others have said, either he doesn't like drop hitches or just wanted something like bike rack (or motorcycle) to be lower as those have ramps that need to reach the ground, have the proper angle for loading/unloading to clear the middle of the bike frame, etc.

I'm assuming that the lower one isn't properly mounted to the frame and can't handle much weight!

JMHO!
Bill

Maybe the previous owner never heard of a drop hitch? Towed two different trailers, and used the same hitch, but the height of the tongue was different for each one. Maybe though welding a second receiver was easier than keeping track of 2 different hitches.

I've seen trailer hitch on the bottom and bike rack on the top,but they're usually separated by five inches or so. Bike rack being in the higher receiver. Personally, I like boat trailer on the back and bike rack in front hitch.

his version of a superhitch 2 square tubes better than one thought

Trailers with different level tongue heights. Much cleaner looking with an adjustable hitch. Also might be used for a homemade step or cargo carrier.