I have exactly this - it's utterly ridiculous since 14.6. My App Store is the top battery use in the last 10 days with 46% of usage and then Messages is next with 8%.
Yet in terms of activity, App Store shows 1 minute (yes - minute!) whilst Messages shows over 4 and a half hours.
Apple have completely screwed up something with 14.6 - how can the App Store use nearly half the battery in 1 minute of use, when the next biggest user ie Messages uses only 8% in well over 4 hours.......?
And frankly these people who reply to every issue with 'backup, restore and new and restore from backup' are adding what value? Seems like they just want to try and get as many posts as possible to bolster their ratings - pathetic.