I am not sure this is going to be fleet-wide. It depends on the ship and whether there is room at the muster stations to store the life jackets. That was my take on Richard Fain's comments about this topic.
Some people can do well donning a life jacket at the drill but will forget it in the heat of the moment should a real emergency occur. Another thing to realize is the need to immediately don a life jacket or risk drowning is exceedingly remote. People tend to get a Titanic mindset about the muster stations, and that is - pardon the pun - going a bit overboard.
We didn't use the jackets for our drill on the Celebrity Equinox preview cruise in July. We went to inside muster stations (mine was the main show room) and they showed a video of emergency procedures, and then the crew did the demo and pointed out the routes to the boats.