Your example uses time.google.com which is a very bad source for an NTP server in the NTP pool. Google uses Leap smear Alas Leap | Public NTP | Google for Developers which handles leap seconds in a totally different way than the NTP protocol does. The NTP protocol adds or deletes one second at the end of a minute, whereas Google smears the adjustment out over a period of 24 hours.
You can find nice plots of the difference between NTP time and Google time in this discussion here: Google Public NTP - #9 by ddrown