Even if Demko stopped that initial shot or it goes wide it allows the player to get in on the forecheck quite easily.
You get in his way he has to go around you. You always see defenseman always locking up with guys right before reaching a loose puck on the boards, then the board battle ensues. It's a similar sort of thing just without that physical side and freezing the puck on the boards.
Edler and Myers are good at locking guys up and making guys who have speed on them go around, allowing time for everyone else to get back on the back check. It's harder for Hughes because he is small but he has the skating to get in peoples way or even getting to the puck first and he didn't do that there and neither did Tanev. Middle of the ice was too open.
Refs aren't gonna give you an interfering penalty if you're holding your ground.