I looked at this case as well. Your first PM on Monday 17th tells your opponent that you cannot play this week before Friday 21st.
Are you really asking why your opponent receives a WO in this case?

@farshad,
The message you sent to your opponent on 18th said nothing more then "add me to PSN...". Your opponent actually offered you a time of play. Then he said: "add me to PSN". Then both of you "having trouble" adding each other to PSN and seem to concentrate on that rather then the obvious, scheduling the match so you both can be there at the same time and actually sort it out, add each other, whatever...
Guys, I am glad you like Moralspain more then me or Cro

What may seem obvious from your side, may not be the case from hosts side. You may spend 5 days straight in-front of PS3 or Xbox waiting for an opponent, if you have not setup time via PM that host can clearly see - he has no way of knowing you are waiting. We have a system in place, use it, it works. Your first PM should include the time when you wish to play the match. Rather simple guys.