I've been following this thread. Waited until my cruise was over (Discovery 1/27/24) to tell our experience:
We booked our Suite on the Discovery last October. Our documents confirmed the complementary 360 experience. A few emails from Princess also said stated we could reserve ahead of time with no charge. Numerous calls to try to book resulted in being told we would be charged up front. I even sent an email to Princess VP and never got an answer. Not wanting to end up with $300 shipboard credit, we decided take our chances to book on board.
Once on board, our Concierge had a very difficult time trying to book our spot. Finally, on the last day he was able to secure our reservation.
Sorry it's such a long story. It did have a good ending, but the process to get what was promised turned into a real challenge.