I'm not sure that he has been using a controversy to sell products as much as he has identified a preference for a style/characteristic of a product and then gradually started to offer them for sale.
Clearly Jan H. gets credit for getting us to talk about frame flex in a positive way, and most of the credit for advancing the idea that high quality larger tires are not slower than smaller tires of the same quality (this summary overlooks the details and caveats, though). He was the first to offer test data that backed up this claim.
Looking back through my issues of Vintage Bicycle Quarterly and an index to articles, I see that it was in VBQ volume 4, number 2 where he has a short article titled "Frame Stiffness Revisited". This was the 14 issue of the quarterly publication. The index to articles doesn't offer any hint as to when/where the stiffness issue was first discussed.
As for tires, issue 13 does have a review of the Grand Bois Cypres 650B x 32 tires. I suppose Grant Petersen gets credit for popularizing the 650B tires and finding manufacturers to source them, IIRC. In this VBQ issue, Jan says that he will make a one-time offer to sell these Grand Bois tires. As such, it doesn't appear that he is simply providing a favorable review to a product that he was already selling. While this issue does include a small ad indicating that Jan was acting as a distributor(?) for Alex Singer cycles, I don't see any sign that he is selling tires or other goods at that time.
I think I've made the argument in the past that the bike industry has been happy to argue that certain bike or component characteristics are desirable without presenting any sort of test data to prove it. It seems like it has been up to private individuals or groups to run some tests to demonstrate what is better or worse. Unless the characteristic is something that the consumer can easily verify, such as weight, the manufacturers don't appear to be interested in performing tests.
Steve in Peoria