@Jörg-VMS-e-V The notification that new maps are available is only visible when you navigate to the section in the menu where you can download the maps. There, you will see that a new version is available. In any case, all maps that you have ever retrieved are redownloaded. It is not the case that only the changed maps are redownloaded.
By the way, you sometimes hear that someone insists on navigating only with the latest maps. I have never been concerned about that because the most scenic roads I, as a motorcycle rider, want to travel on have existed for years and have long been incorporated into the maps. It may well happen that I am a few map versions behind.
However, if you use the app solely to navigate from point A to point B and you do need access to recent map data, then you should regularly check if there are new maps available.