Unfortunately it is not really uncommon. I see the same thing with any adblocker that uses VPN as well as my actual VPN app. I believe that the graph can be safely ignored though as the way that iOS reports battery usage, it will think the adblock VPN app is using the most because all data is redirected to that app to work. It looks bad but I believe it is just a benign reporting. Of course, if you physically see your battery depleting quickly, then there might be an issue. Likewise, I know earlier beta builds of iOS 15.4 had "Okayish battery" life to begin with.