Just update, and don’t worry about it.Some people reported a serious battery drain on 13.5.1, then 13.6 fixed it for some, worsened it for others, and now that 13.6.1 apparently solved all the issues, some people experience an even more severe battery drain.
Honestly I have an iPhone 8 with iOS 12 and I want to update to 13 but at this point I don’t know which one to install, 13.6, 13.6.1, or just keep waiting...