Timezone is not updating with WiFi and ethernet network in Android
Time synchronization via Wifi/Ethernet bases on the NTP protocol. All NTP server are running with UTC time, hence they can not provide a time zone.
If if they would the time-zone would be useless, as an NTP server can be located anywhere in the world. Typically one NTP DNS name consists on multiple NTP servers, and based on a region the closest server is selected, but that still does not mean that the server is located in the same time-zone as you are.
Only the cellular network has the Network Identity and Time Zone (NITZ) service which provides not only time but also the current time-zone. As a mobile network cell is limited to a very small area it is possible to deliver correct time zone data via cellular.