Did you set login password or fingerprint ? It the initial security phrase when you reboot. After which once you enter your pin the clock style revert back to the one you set.
Unless you use their default clock style
Ok I just confirm is a security feature. I disable fingerprint and lock screen pin everything is ok . Once security feature enable the lock screen will default initially till we log in
Sent from Samsung Note 20 Ultra [SD] using GAGT
I'm using fp, yup, I'm using one of the clock style from Samsung.

Of course no phone is perfect lah. I admit the 11 pro max battery was good. But signal very bad! Marina sq basement 1 bar only whereas my ROG Phone 2 (at that time) had full bar signal! Both using singtel!