He agreed to a deal with a seller and once escrow was setup he backed out of the deal. This is a sign that he was trying to avoid using escrow and only agreed to accept escrow to avoid setting off any red flags to others. Despite this being a bad idea, often times people will simply agree to trade without escrow if one does not respond and setup escrow quickly enough.
A neutral rating is more appropriate then, since no coins were lost and no scam was attempted. People are allowed to back out of deals. You should put in the rating your belief it's a sign he was trying to avoid escrow.