He just takes (on average) 4.53 more turns in games where he's losing
Yes, I don't surrender until the game is absolutely, unequivocally over. In my opinion, not the opinion of my opponent or others. The reason is that I regularly end up winning when I was in a seemingly hopeless position. Often because my opponent ends up surrendering when they shouldn't have. A lot people seem to think if I break one of their bonuses, they've lost. People also make mistakes. If I'm playing a mediocre or poor player, I can hold out hoping they'll do something dumb, like use one of their giant stacks to make a 150 blockade or something.
I don't consider that stalling at all, I'm trying to win. Just because the other person has an advantage, even a large advantage, doesn't mean I need to give up, like so many people do.