This. Also, I would think that DCL has a greater number of young children than other cruise lines. Navigating with young kids in a crowded area, and keeping kids occupied while listening to directions, is much more difficult than going to the muster site when convenient. It's important for guests and crew to know what will be particularly difficult in the event of an emergency and who might need extra help.
It's also important to see the passages that will be used during an emergency that aren't normally open -- several of my "optimal paths to muster station" have gone through crew areas that are accessible to guests only when staffed by crew members and wouldn't be open if guests had a period of several hours to go to their stations. DCL can station people all along the paths because there is almost nothing else happening around the ship during the muster -- no food service, no entertainment, no room servicing.
