I have a TP-Link Archer C6 v3 and two TP-Link EAP235-Wall devices running on my network, all of them running the latest stable build of OpenWRT (22.03.3 r20028-43d71ad93e).
I noticed on the EAP235-Wall devices I have an additional "Time Synchronization" Tab in my System page. (System -> System -> Time Synchronization)
This tab is missing on the Archer C6. What is the reason behind this?
Try making a backup and then resetting the device to the default configuration. See if the tab comes back. And if it is back, then restore your backup and see if it stays there.