Other than the two individuals involved, no-one really knows what’s gone on.
If the bearings are genuinely knackered then it should have been made clear from the outset and the seller ought to put his hand up to it and sort it out (ie a refund).
If on the other hand (and if I had to make a bet, this would be where my money is), the buyer is about as mechanically minded as my 5 year old and has been fed a line by a shop mechanic. Instead of trying to resolve this sensibly he has resorted to flaming the seller on a forum. Shame on him, very poor form. However, clearly he’s a little on the dim side to have posted his phone number and work email also so it is only to be expected.