That has been alleged.
Film historian vin KeBrownlow repeatedly criticized the book, citing Anger as saying his research method was "mental telepathy, mostly".
I believe the chapter on Thelma Todd contains stories that came from things that were misunderstood or distorted in retelling, because they appear to be strangely garbled versions of the stories that we started out with.
The authors of this book, Patrick Jenning and Marshall Croddy, also felt that these things were misunderstood or distorted in retelling.
So that is something that we agree on.