This blog post covers the various techniques to sync clocks in general (NTP, GPS clocks / TrueTime, Timestamp Oracle, HLC, etc). CockroachDB uses HLC (hybrid logical clocks), which is the same clock sync mechanism as YugabyteDB uses (and Apache Kudu as well).

The page you linked to talks about how HLC is used to get distributed transactions to work, and there are differences here between the different databases (Spanner, CRDB, YugabyteDB, etc).