So they were "very disappointing", but not "very disappointing" enough to refuse a free pair, at their expense?
> That manipulation technique
Perhaps, since you were happy to accept the headphones, they believed your original negative review was not sincere, but itself a manipulation technique to get a freebie or special offer in return for a more positive review. (Which I suspect is not unheard-of for some buyers on Amazon.)
To be clear: Although I don't know you I don't believe that is what you did (most people don't do that), what I mean is the company may be used to some people trying that kind of thing, and accepting the product for free may be a hint that you're willing to do what they asked.
However, what kind of "positive review" did they want? A review where you pretend not to be disappointed, or simply an update to your review stating something like: "while I don't believe these are worth $65, and returned them, I can't fault the customer service in trying to make up for my disappointment"?
Because I don't see anything at all wrong with the latter; and it's certainly more reasonable than leaving a negative review of a product which you were happy to accept at the 'right price'.