Having access to the GPS system on your phone doesn't necessarily mean that they are storing the exact GPS coordinates where you validated your tag. They could be using it to geocode the nearest locale (town, county, etc..). If you notice on your validated tags it shows the nearest locale, so at...
Make sure you can log into the app before going out of service. I had a couple issues with the app requiring me to login when out of service and that obviously is an issue. To be safe I took screen shots of my licenses and tags.