> Just like rephrasing A Song ot Ice and Fire a bit, and switching to a different language, doesn't remove its copyright.

There is some precedent for this, e.g. Alchemised is a recent best seller that had just enough changed from its Harry Potter fan fiction source in order to avoid copyright infringement: https://en.wikipedia.org/wiki/Alchemised

(I avoided the term “remove copyright” here because the new work is still under copyright, just not Harry Potter - related copyright.)