He is "recalling" from other information at the time. I don't think most apple products were for sale on Amazon at that time, but that's not really what he's talking about.
He's referencing that other ecommerce sites (e.g. walmart) couldn't just say "oh, one click buying is a good idea, and an obvious one, so we'll implement it too". By having Apple pay significant money for right to use the patent, it adds validation that it isn't a frivolous patent, and actually a useful, non-trivial, non-obvious solution which warrents being licenced.
It gave Amazon much better ground to file patent infringement against any competitor that attempted a 1 click checkout solution without licensing the patent, both improving chance of further licensing and reducing the chance competing ecommerce platforms would implement the feature without licensing it through Amazon.