Yeah, this is actually very true and commonly overlooked, as people don't think that they need to go further than just looking at the anchored research options such as clickbank and such.
It isn't just about what is hot and selling but more about who is actually buying it.
Anyone can promote a general niche product to the general niche and make sales.
The thing is to actually break it down into sub-niche research and see who is buying more of those types of products within that given sub culture...and even more importantly, the " why " as to their need for that purchase.