Coincidence isn't a rule to make every determination by, but there is no reason it can't be a factor. That being said, from what I have seen, Cars.com has been very active, possibly to the point of aggressive, in using this company to perform studies with the dealerships recently. I thought I even saw that they were offering to pay for the studies for the dealerships to participate. Although in and of itself there is nothing wrong with that, what are the odds Cars.com would be asking their dealers to let them pay for a study that had any chance of showing negative results? Even if you buried a negative result from the public, all of the participating dealers would then turn around and demand their rates be cut and have proof to do so, Autotrader and Gurus would have free marketing material against Cars.com, and Cars.com would never use this company ever again which is lost revenue for them.
These studies and subsequent positive marketing material were churned out very quickly, which again isn't impossible, but in a scenario where the outcome is supposedly unknown, it should take longer than usual to produce material for public consumption not less.
From what I can tell, if a dealership wanted to confirm these results personally they couldn't. The company states clearly on their site that the information about people they obtain from I.P. addresses cannot be shared by law. So, dealers have to trust that the information they got from the I.P. addresses matched customers who actually purchased vehicles. Again, this is just what I "see", so I could be wrong. But it's up for you guys to decide if these companies are producing what they claim to be. If so, they deserve credit for working hard to solve a big problem.