What does "network time" mean on a WiFi-only device?

I have a tablet (no phone network, just WiFi) running Android 12. In the Settings | Date and Time sub-dialog when I select Automatic date & time, there is a 3 way choice: - Use network provided time - Use GPS provided time - Off What does the first option mean? It sure sounds like NTP, but there is no interface to pick a NTP server. Some wifi routers provide a NTP server address with their DHCP replies, but I don't think mine does, and in any case a mobile device can't rely on that, right? Strangely on my phone, also Android 12, the Automatic Date & Time widget is just a binary switch, on or off (though the phone definitely has GPS). I think "on" here means the mobile network. But how come this interface differs between two devices with the same Android release?