What is happening in the log line from /var/log/syslog

[reader]

ubuntu 20.10

I see these log lines in bunches periodically in /var/log/syslog

  Apr 24 10:07:11 2x systemd[1]:
  boot-.zfs-snapshot-autosnap_2021\x2d04\x2d24_13:30:03_frequently.mount:
  Succeeded.

I had sanoid installed at one time but did `aptitude purge sanoid'.
Which appears to have removed the systemd timers

I still have sanoid running but from a git clone of git sanoid repo
installed by hand but without any systemd timers.

Relying instead on good old cron to call sanoid.  It calls sanoid
every 15 minutes, which does not match with the timing of the syslog
line above.

Can anyone say what is actually happening there?  Why would snapshots
be getting mounted?