Timman quotes Larsen (an article in Chess in Canada) as dismissing the story - "incredible nonsense" - but then devotes two paragraphs to citing Karpov in its support. Karpov's account is the one given here as coming from his autobiogaphy, Karpov on Karpov- (Timman says it is from Russians Against Fischer, and the two accounts, though using similar phrasing, are worded a bit differently, presumably because they used different translators.) Timman then says "what Karpov writes about the three promised tournaments is correct", mentioning Hastings, the IBM tournament in Amsterdam and Palma de Mallorca.
I admit that my strong inclination is to back Larsen rather than Karpov here, not least because
- it is 45 years since Korchnoi left the Soviet Union and only five since he died, and therefore he had forty years to complain about being instructed to lose a match.
- There is also a total absence of any evidence to back up the story - "no documents exist to substantiate this plot" as Karpov admits (or "no documents confirming the deal", if you prefer the NiC version). Again, it is thirty years since the USSR was dissolved and this is plenty of time for contemporary records to be found, and for that matter for people who were party to any such decision to speak or write about it, or for their own personal archives to be read.
- The "three international tournaments" evidence isn't really evidence of anything at all, unless we can show that the story pre-dated his being sent to those tournaments, as opposed to emerging afterwards.
That said, I've not read Russians on Fischer, nor Karpov's autobiography, nor (as far as I can remember) Korchnoi's. Timman's article, by the way, is an excerpt from his forthcoming book on the 1970-71 qualifying series.In the absence of any real evidence to the contrary, Korchnoi’s conclusion that both players played the match in good faith cannot be challenged.
[* this reads to me as if something were being quoted, though if that is so, I can't see what.]