Or they just lie to you 'we need your location data to do <sensible thing you want>' (like say localized weather or nearby starbucks or whatever) however they then turn around and basically track you constantly and sell your data to all comers.
That said, the attention of the blog post seems to have triggered them to disclose now on the Apple [1] and Google Play [2] store that they are indeed collecting your location data. They got away with lying for quite some time, over 100k downloads on Play store and 1.57k reviews.
[1] https://apps.apple.com/au/app/battery-monitor-bm2/id11154920...
[2] https://play.google.com/store/apps/datasafety?id=com.dc.batt...