Keith -- I'll try to locate some paperwork on them.
They're no help in fueling, since there's nothing to hold onto when fully up on the step -- it could be done but would be tricky. I did use them once for fueling at an automotive station at Denio Junction NV from six gallon fuel cans. Hoisting them up and keeping my balance was a tedious and marginal project. What they're really handy for is dumping the fuel from the Gats jar and checking fuel level. Also for checking to make sure the caps are secure after getting fuel from a truck.
I've been to "Denial Junction," but never bought fuel there. The last time was after overflying Geek Week (er, I mean "Burning Man") and Soldier Meadow a year or so ago.
The last time I climbed on steps on a 150, I stuck fingertips into the recess around the gas cap for the last part of the climb. That was a few decades ago.