Let's see if I can put this in basic terms for you.....
Erza says, I'll win next time which is a concession. No matter how you try to spin it, Erza concedes and Laxus then says, "That's my line" and collapses instantly later. Laxus doesn't even try to acknowledge this fight, he concedes in a sense too making it a double ko.....aka a tie. He also says he ran out of magic and still couldn't stand up......Laxus did not win that fight.
Also doesn't help your case when the person who was literally watching the entire fight calls it a tie.