WOH goes by check out date to determine in which year nights are credited. By adding the night of the 31st to your existing reservation you caused the entire stay to be allocated to 2023. Some people do this intentionally so that nights from the previous year get credited to the next year and they then have a head start on requalification. There are a number of threads that discuss this.
Here is the most recent:
https://www.flyertalk.com/forum/hyat...qn-2022-a.html

While years ago they would sometimes split the nights up, I can't say that I've seen many reports of this in recent years. All you can do is ask and see if you can find a sympathetic rep.

You would have been better off to stay somewhere else or to book that one night stay on the 31st in someone else's name.