Eicar virus detected immediately when saved although on-access scanning is disabled, but NOT detected during on-demand scan?

I just installed sav, but on-access scanning is still disabled:

/opt/sophos-av/bin/savdstatus -v
Sophos Anti-Virus daemon is active
On-access scanning is not running

I tested it by making an eicar.txt file in Documents dir and immediately when I saved the file, I got Sophos anti-virus alert saying that EICAR-AV-test detected in file ...

How is this possible if on-access scanning is not running?

After that I tried to run on-demand scan

savscan ~/Documents

with default settings but it did NOT notice the eicar.txt. Why is that?

This is Ubuntu 16.04 LTS

Thank you for your support.