I had a another look, when clicking the details there it looks like it is taking purchase history for the financial information. It mentions about analytics purposes. I guess its just for keeping tabs the number of purchase for the app. That makes me think perhaps at some point the app (boost for reddit) was designed to track a subscription like system but nesr the end they just decided to just go with one time purchase, and it got a carried over with this new app. Then again I’m not familiar that much with app development if it really need that permission to keep tabs for purchases.