I saw them review the play in question on one of the NFL studio shows on ESPN or maybe NFL Network, and they were discussing it as a legal block. They didn't say specifically, but I got the impression that because the action was moving away, that's what made it legal. The former player said that the league was going to review the rule next year, but seemed against it being changed. They said that when it was brought up before, too many coaches and players said it would have a very negative impact on teams ability to run the ball.