GunnersWillys,
That sure looks like PO repair work to me. The fasteners do appear to be placed to hold the panels down flush with the tub.
This is an image of what Classic Enterprise offers as a replacement of the step:
https://www.classicent.com/products/jeep-step-treadSome images from the CJ3B Page of Lawrence's '55 showing the step and that corner of the tub (drain hole, etc) and wheel well:

Notice the small "tab" sticking out of the back of the step flush with the tub.

And yes, the hat channels run right out under these steps to reinforce. There's one bolt/nut that secures the back of the fender to its front edge.
I've seen examples of repair work where that step is brought straight back (like yours) to connect to the tub. If I were to guess, I'd say it's easier when constructing; less bending and fabricating. Also, after market tubs don't seem to have the drain holes in the tub either (easier to make) but if yours is skinned, maybe you can see them from inside. do you ever collect water inside on the floor?