Yes it is possible but not from the interface. You have to sacrifice the vibration from the quiet settings. It seems that the full profile is built in a down to top logic. So full includes the quite profile. And the quiet profile has vibration on. If you remove the vibration from the quiet profile, then vibration is not present in the full profile and you are done.
cd /usr/share/feedbackd/themes/
cp default.json default-orig.json (for backup purposes)
open the default.json file for editing as root (say sudo vi default.json)
scroll down to the quiet profile and locate and delete the section:
{
"event-name" : "phone-incoming-call",
"type" : "VibraPeriodic",
"duration" : 10000
},
being careful to preserve the format of the file. Save and reboot.
Now you will be receiving calls without vibration, only sound.
This will be overwritten with any update of this file and you will have to re-do it. It is supposed that if copied in the .local directory of the purism user then the setting will persist but I did not manage to do that. It seems that this is ignored if set for the user and not systemwide as above.
In any case this is a solution.