Pretty sure that his point in bringing that up isn't to say that what they are doing is unethical from a FOSS point of view, but rather he was making the point that it is entirely within Amazon's technical prowess to make their content available on Android devices
I think the addition of the phrase, "thus benefiting from Google's work", refutes an interpretation of purely technical capability. If that phrase had been omitted, I would be in agreement with you and would have had no reason to comment.
