Kurviger does not use Google Maps. Kurviger uses data from OpenStreetMap. You will find differences between Google Maps and OpenStreetMap data. The biggest difference is, that if you find an issue or something missing in OpenStreetMap, you can fix the issue yourself or you can tell the community about the issue and they will help to improve the situation. If you see an issue with the routing, you can also improve the situation yourself.
For more details, please have a look here: There was an issue during the route calculation or navigation, what can I do about it?