Not quite right, the intermediate gates are the 'normal' gates which allow boats up to 62', the outer gates allow boats up to 80' but as they are pointing outwards normally mean that they are used when locking down but as a last resort the hydraulic rams will hold back a couple of inches in the lock to allow the gates to be used to allow longer boats to lock up when the falling tide does not quite make a level,.
One point to note, although the lock is a wide lock it will not take two boats at 62ft , we had trouble (as seen on the video) with a 50' and a 60' boat getting jammed up for a while! due to the geomatry (sp) of the lock.
Tim