Given the lack of proper color-coding, and pieces of wire nutted together to extend wires, I can guarantee that my A-frame's (2014 Rockwood A122) as-built condition does not match any wiring diagram that exists.
That is the real reason why FR does not release wiring diagrams - if they actually exist. If they used standard wiring harnesses like those used in automobiles, then a diagram makes sense. But with the variety of options that affect the wiring, particularly dealer-installed options, keeping a wiring diagram current and correct would be a nightmare.
Working in aircraft maintenance, where drawings have to be maintained, drawing maintenance is one of several factors that makes owner modifications very difficult and expensive.
2014 Rockwood A122 A-frame
2008 Hyundai Entourage minivan