How about Dave Pelzer's "A Child Called It" series? Even his brother called him out on it.

I'm wondering if the example about Amadeus really counts. Did the creator ever try to present it as factual? I know a lot of people have challenged it for being essentially made up, but I'm pretty sure Peter Shaffer never tried to put it out there as 'a true story,' as it were, which he would need to do for it to fit this trope.