Where does it say he bought any 'later ones'?
He could have read reports of 'later ones' sucking. Credible reports.
Had your theoretical scenario been the case I'd think his wording would/should have been more like "I have read/heard—from what I deem to be credible reports—claims that the later ones suck." In an audio forum discussing gear, if a poster says "this unit(s) sucks" I assume it's their opinion on the matter after having evaluated it, or they'd say something like "according to reviewer/source XYZ, they suck".
[Also it would strike me odd that a person would ever post claims of others, stated as a matter of fact—"they suck"—from sources they felt were
not credible, so doesn't that part of your hypothetical scenario (where he's simply reporting what he's heard/read) pretty much go without saying?]