This argument seems sound.
Amazon is not a neutral entity or a public space. It's a private platform with its own interests that are very often in conflict with sellers.
There is this weird cultural expectation of platforms and platform-like applications (social media, multiplayer video games, online stores, proprietary libraries/engines, even entertainment media "universes" and franchises etc.). Participants and consumers seem to think that these platforms are somehow public spaces that they partially own, or at least they act that way.
But you only own what you actually own.
There are legal instruments and structures that actually let you partially own things and/or grant you rights so you can act on these kinds of expectations: coops, open source and other such licenses etc.
When internet culture and commerce wants to mature, then maybe we should start focusing more on building on _legally_ trustworthy foundations.