I think that coaches announced 14, because in weekend there are 3 matches, so they can change something in roster. In every match coach still can have only 12 available players, including 1 or 2 liberos.
Yeah, that's right and actually this rule is not new - it was the same before, too. Coaches could choose 14 players for whole weekend and from these 14 players they chose 12 for every one of the two matches, so they had the opportunity If they were not satified with the game of one of the players or some injury happened on Saturday's match for ex., to replace him with another player (from the 2 left out of the group for this day) for the match on Sunday. Groups for the matches were confirmd literally few hours before the start of the day's match, so there was always speculation about exactly which two players won't make it to participation today 
