The cloud time sync is done a CoAP packet on the regular cloud connection. There is no NTP in Device OS for time synchronization.
However, if you have a Particle cloud connection failure, there is an internet test that makes an outgoing NTP UDP request (pool.ntp.org, port 123) to see if you have working DNS and Internet to other hosts. If you have this blocked, the cloud connection will still work, but it will affect the logs,