I'm guessing the hand truck (furniture dolly) shown in the pic is simply to represent the frame, but is not the frame itself. Either that or it's going to be altered...
The front axle beam, knuckles and spindles I used were straight off an old lawn tractor that I molested for parts- bushings included. I installed the beam inclined rearward at 5 or 10* (can't remember now) to get the caster angle I wanted.
Only now that you mentioned it can I see that it is a dolly. You are probably right....it is probably just for mock-up or will be changed.