It is not a surprise, it is already happening. You can turn it off, but AFAIK if you don't it collects this information even if the Google maps application is not open.
From my personal experience, I have an Iphone and it asks me about once a week about Google Maps using my location in the background and if that is okay. I always tell it no. I didn't know I could turn it off directly in the app, thank you for the information.