"Fundamentally fine"? How do you think Amazon would react to someone scraping their marketplace and posting the inventory under their own service? Unless the answer is "they'd be perfectly happy to have to opt out individually in each case", that's a double standard. The only reason they wouldn't actually need to care about this is because they have comparatively inexhaustive resources to be able to shut this sort of thing down with a sledgehammer without having to risk meaningful consequences rather than what they're telling sellers to do, which is to ask nicely to stop being included, and that's a sign of an unhealthy ecosystem where competition is non-existent.