You are correct about how it works. Companies have (or buy) geo-ip data to correlate ip addresses with real world locations. These databases change frequently

You are correct about how it works. Companies have (or buy) geo-ip data to correlate ip addresses with real world locations. These databases change frequently (IP's bought and sold, people's residential IP's changing). There's a couple possibilities about why it is different. Maybe the maps app actually goes through Apple first, and there is a slight flaw in the most recent version of Apple's geo-IP database. Even if they both query Google for the location, it's possible that different sets of servers serve the mobile maps versus the web maps, and they are slightly out of sync with which databases they use.