That's a feature sellers can opt to use.I think a lot of the 'offers' being sent are from ebay rather than the seller.. you don't have to be watching something anymore to receive an offer.. even if you just click on something an 'offer' will come through within 24hrs.. i think this is ebay removing the buyers fee and sending the offer for the sake of a sale.. hence why sellers have no recollection.
I might check that then and turn it off.
Then again, it hardly matters if I was prepared to take that amount anyway.