Most the cases are sealed and depend on self reporting to the media by parents who do so at great threat of it impacting their secret proceedings, where you cannot even face the accuser.

By design they've made such studies effectively impossible from the outside. You don't even get a jury. So we're left with the odd anecdotes (as exemplified below in sister comment)from those who weren't successfully intimidated.

And that's the beauty. They can knowingly and willingly intimidate parents while screeching "but muh data, you can't prove it" laughing all along by design they've hidden the data in the shadows from inspection.