What's quality_1vs1 really shows?

[Ghotrix]

I've simulated a match of 10000 games between players A and B. A is stronger than B and is expected to score 0.71 on average. Given that the expected score and win probability - P(W)=0.5, P(D) would be equal to 0.42 and P(L)=0.08. Yet the simulation result shows quality_1vs1 is equal to ~0.882. Am I misunderstanding quality function or it's something else?