Going back to this point. I have personally experienced this on a September 2021 sailing around the British Isles. My husband had the full drinks package while I only had the soft drinks package. However, I was visibly pregnant so it was clear that I would not be drinking at any stage of the trip.
I asked bar staff as soon as we got on board but it had to be run by the one of the bar supervisors so we couldn't actually buy the package until the next day which wasn't a problem since we would have struggled to drink the $69/$29 package costs on embarkation day. In fact, a lot of the bar staff were advising people not to buy on the first day because of this.