That language is misleading: only AMP articles are eligible for "Top Stories" placement, which means non-AMP results are completely excluded from the most prominent ranking on SERPs.
AMP may not be used as a ranking factor within each class of results, but it absolutely creates two distinct classes of results, where AMP is given priority over the open Web.
You're right in that I really shouldn't be directing that at you. I believe that you, personally, are trying to do the right thing. Apologies for the snark.
However, I believe the Google devs behind Froogle also had good intentions. They provided a framework to make product pages easier to consume for Google. They provided a real incentive for publishers to conform to that standard. They got nice placement in a carousel, cached display of product images, and so forth. Then, later, well...
Edit: And whatever the technical reason for the google urls, it does open up possibilities for the future that aren't desirable. It's a dangerous precedent.
AMP is not a ranking factor and so the percentage of results it makes up is largely a factor of the percentage of publishers publishing AMP.