This seems incredibly unlikely. They all want clients to have accurate time, because it underpins things like sessions and TLS certs. It would also almost certainly be trivial to proxy back to regular NTP.
Even if the NTP pool somehow died, all it takes to make your own Stratum 1 NTP service is a GPS chip. An old phone probably makes a great small-scale NTP server, or an ESP32 with a GPS chip attached. 20 years ago it would have required exotic parts, but they're mundane, cheap and omnipresent these days.
Even if the NTP pool somehow died, all it takes to make your own Stratum 1 NTP service is a GPS chip. An old phone probably makes a great small-scale NTP server, or an ESP32 with a GPS chip attached. 20 years ago it would have required exotic parts, but they're mundane, cheap and omnipresent these days.