The watches/clocks they are talking about listened to WWV, a set of radio stations transmitting from Fort Collins, Colorado. The system long predates the Network Time Protocol you’re referring to. Radio controlled clocks/watches had no means for accounting for latency.

Sync process? The other comment was talking about the old receivers for the atomic clocks on SW/MW frequencies. It was a one way thing.

Now in theory if a receiver also had GPS they could account for the distance. But, then they’d get far more accurate time from the GPS receiver so…