Thank you for reaching out. I can certainly understand your concern with your watch face customizations not syncing between your phone and watch. If you want to transfer content between your Samsung smartwatch and phone, the two devices must be paired through the Galaxy Wearable app on your phone. You may also need to allow permissions for certain apps. If you are still having some trouble, follow the tips below. Give this a try for some tips and trying to get your features to sync: https://www.samsung.com/us/support/troubleshooting/TSG01003149/
Next step I would recommend is making sure you are saving the customizations for the watch faces inside the wearables app before closing out of the watch face. Give the section on customize watch faces using the Galaxy wearables app a try using this link: https://www.samsung.com/us/support/answer/ANS00080308/
You can also use the link above to learn about customizing the watch face from your Galaxy watch 4 classic directly.
Are you using third party watch face or stock watch faces when you are experiencing these symptoms?
Have you been experiencing these symptoms recently such as after an update or have you always experienced these symptoms?
What type of device are you pairing your watch with?