Have you checked and made sure that the setting is ticked to show on the calendar? I think there is also a setting in Google account to select the country for which to show public holidays.
I use this feature as well and what i have noticed is that if you are actively using the phone when the scheduled time hits it will not automatically switch between the modes until you lock and unlock your device.
I agree. The foldables are nice, but they just seem like a gimmick. If you use your phone often then you will be opening and closing it multiple times a day, which will eventually wear out the hinges. I also feel like It would eventually become a nui...