> “well I went into a dark room with only the first Harry Potter book and a type writer and reproduced the entire work, so now I own the rewrite”

This is not a good analogy.

A "rewrite" in context here is not a reproduction of the original work but a different work that is functionally equivalent, or at least that is the claim.

To stay with the analogy, Harry Potter is not a rewrite of A Wizard of Earthsea, even if they both contain schools that teach magic.

Possibly important is that it’s largely api compatible but it’s not functionally equivalent in that its performance (as accuracy not just speed) is different.