I went to look up something on IMDb, and then I immediately got an email saying I registered for a new account. I probably did have amazon.com open in another browser tab, but I did not take any actions to created it. From what I can gather Amazon linked accounts are a new thing.

The normal steps to delete an account don't work with Amazon linked accounts, and they send you to amazon.com account settings, which of course, is impenetrable. The Amazon customer service human did not even know what IMDb was.

Just a warning. This is something different than a dark pattern or enshittification.