I am not sure if this is new or happens on some queries but Besian Sopa posted on Twitter a screen shot of a Google Maps Local knowledge panel showing a circle in the map versus showing the typical marker pin icon.
Here is a screen shot from Besian who where we see the circle pin:
When does Google show the circle version?
Forum discussion at Twitter.
Mike Blumenthal said on Twitter that the circle happens when it’s a SAB and address is hidden.
