Not sure it's clear what you're getting at. If the BR is in the correct place (running lane) I've got nothing regardless what the catcher does or doesn't do. BR has to be somewhere and that's where she is protected from interference. Maybe I'm not understanding what you're asking.It isn't the catcher moving, it is the delay in the throw. What would you have if the runner is in the same place, the catcher DOESN'T move to open the lane but hesitates just for a moment because of the runner, makes the throw straight down the line and the same runner safe on a bang-bang play?