That's true when you stroke toward the object ball and there are no nearby obstacles to prevent the OB from moving freely away. In this case you're stroking away from the OB so that principle doesn't apply.
There's no push when you stroke toward the object ball, the same as there's no double hit. It's an entirely legal hit. But in this case it's the rail, not the OB, that might cause the foul.
He didn't scratch, but the shot could have been a double hit or a push if the rail prevented the OB from getting out of the way of the follow through. I don't think this happened because of the wide angle the OB was hit into the rail, allowing it to rebound freely away without being "trapped" by the tip.
It's an interesting shot - actually a kick shot.
pj
chgo