If a 1900 bkr beats a 2200 bkr, then it is called luck. If a 2200 bkr beats a 1900 bkr it is called skill.
But the better point is that a person with a 2200 bkr probably got that by being lucky themselves anyway, so doesnt it all work out in the end? On this site, at least after a person has played a certain amount of games, the person with a higher bkr is probably a better player, yet having a high bkr doesnt mean that they won all their games by skill alone either!