The advogato [post is outdated. Since them quite a few things changed. Look at the code and the manual page:
ntpd uses the adjtime(2) system call to correct the local system time
without causing time jumps. Adjustments of 32ms and greater are logged
using syslog(3). The threshold value is chosen to avoid having local
clock drift thrash the log files. Should ntpd be started with the -d or
-v option, all calls to adjtime(2) will be logged.
After the local clock is synchronized, ntpd adjusts the clock frequency
using the adjfreq(2) system call to compensate for systematic drift.
Again, for the majority of use cases, OpenNTPD does achieve an accuracy that's good enough and even better than that.