My first 4 RVs were all like that. A bundle of manufacturer manuals for components and virtually nothing about the RV itself. When I wanted to find the wiring diagrams and contacted one I'm pretty sure the guy was laughing on the other end of the line. Same when I asked about specs for the aluminum frame so I could mount something inside. So when I started shopping for our new Class A I was thrilled when I came across Winnebago that posted all of their schematics, plumbing, electrical, etc. online and kept them for all previous models.
They still do this, the towable division units manual is generic to all it seems but its very detailed. So it can be done, buyers just need to demand it and buy from the manufacturers that supply it. Of course that probably means parting with more money too.