i would say it has something to do with polling rates,
what i mean is some systems (security systems) have polling rates, set time frames where systems MUST report if not these types of alarms are sent.
also WFAM Romtecks are wireless based on mobile phone network, the old systems used standard phone lines where you would get "line open alarms" which is the same thing, system not reponding.
I think correct me if im wrong