It is not a bait and switch. They changed the policy based on an occurrence where they had problems with an adult harassing a teenager in the teen club space (possibly with other situations as well, but that one for sure woke them up as to the possible liability of allowing adults into spaces intended for minors who are unsupervised by their parents)
Bait and switch appears to allege fraud - they let you book knowing full well they were going to change the policy. If I were affected by this policy I would let
DCL know via phone call or email that not knowing when or where you can drop your kids off at the clubs does not assist you in planning adult activities.
Disney does appear to be booking this so that there is always a space for parents to drop kids off (except for embarkation day when both clubs have open house), that will be secure with no outside adults permitted. The problems most posters seem to be having is 1) they are afraid there will be too many kids in this space and 2) they are afraid there will not be age-appropriate activities for the group that was meant to be in the space that is currently not secured.
Currently I think they're doing the best they can to split between the parents who want to go to the clubs with the kids and the parents who want to drop their kids off, but they could make it more clear to the parents how it's going to work. It was my impression that since the clubs were originally meant for parents to drop their kids off, that there would be few open houses, but apparently they are trying to accommodate parents who won't or can't allow their children to go to the clubs without them.