the video was filmed on kronos 1 and the technique worked for me on kronos 2. he isn't doing anything special, just standing in a particular spot.
this is a well known issue between mac clients and mangos servers. one of the leading hypotheses is that the player is loaded before the transport. see Lillecarl's post here: https://github.com/cmangos/issues/issues/198
by standing in the exact spot shown in the video, you can get caught by the walls in the back room, thus keeping you on the ship. as others mentioned, nost had their own fix for this, so hopefully this will be a non-issue when the server releases.