They can be, and are, useful. I've used their info, and the knowledge I learned from them to help buy several rigs now.
I've been a member (off and on, mostly off) over the years.
No they don't just collect sales flyers; they inspect rigs, visit factories, ask owners, etc
No they don't buy rigs, but they do talk to people that do.
One of the publications I bought from them was a book on how to inspect RVs your self. Knowing how to look for quality and how to tell what was "good" and what was "bad" is really useful.
Bottom line, they are a tool to help you make a wise choice.