Blitzcrank's w and recall interaction

So I was playing Blitz on the rift earlier. I had activated my w during a team-fight, the team fight was soon over and I had gold to recall with. So I immediately begin to recall. Any who, the slow happens and it stops my recall. It really didn't affect me all that much, our map was lit up like a christmas tree. I don't know if this is an intended function of the w. So I figured I would post it here.