I've had an issue where, when clicking a "locations" link on a web site, Google Maps "permanently" added a bunch of locations to my map. This was quite unexpected on my part.

(I think it was for a chain or churches or a similar civic organization)

IE, I think someone made a group of locations in Google Maps, and then for the "Locations" link on their website, just linked to the group of locations in Google Maps. In the browser, this works fine, but on mobile, Google Maps just imports the link to my account without asking.