I've been amusing myself imagining the type of scenario Tom Sykes describes, where his editor sat him down with a lawyer and the MS and went through it with a fine-tooth comb, weeding out inaccuracies and embellishments, and urging him to contact literally everyone mentioned in it to send them the relevant extracts of the MS to check they agreed with its accuracy (which leads to some quite funny moments, where his drug dealer has no issue with being depicted as selling him vast amounts of cocaine and ecstasy but objects to being depicted as using non-standard grammar.)
I assume part of this editorial 'paranoia' was because it was a memoir which contains a lot of drinking and drugging at Eton, then in his life as a journalist in NY, so potentially high-profile, litigious partners in crime, and because he was a gossipy journalist with an eye for a good story that might not be true, plus he was off his face for the vast majority of the events he's writing about, so recollections might vary etc.
One assumes that, apart from the post-James Frey paranoia calming down, that the reason something similar wasn't done with TSP was precisely because the Walkers were very much not hard-bitten, ritzy New York Post columnists doing coke and getting thrown out of clubs. They were sweet, wholesome, adorably homeless wild campers who listened to the cricket and watched bunnies hop about their tent. Plus, most of the people they write about they don't know by name, because they're chance encounters on the path.
But yes, can you imagine an adversarial publishing lawyer sitting down with SW and her editor and saying 'OK, first of all, I need all the real names and paperwork for the court case you describe, and then, even if it feels insensitive, I'm going to need to see proof of diagnosis. Then you're going to have to send the relevant sections to Cooper, Polly, Jan, Anna, Moth's brother, Dave and Julie, your children, the manager of the Treen campsite etc.'
What on earth would SW have done?