It should be a feature bullet point on next updates, “this update will NOT drain your battery life”, because come on, why is it always the case. Sometimes I have been affected, sometimes I’m not, so I’m inclined to believe that it is the case when users express so.
I have had that issue and have pinned it to bad app agents, in my case I noticed that using RunKeeper on the watch would suddenly trigger the phone’s location icon even hours after the run was done, session saved and app suspended. So if you can, try to thin down all watch apps, background refresh thingies, etc that jump from the phone towards the watch from the start… I took out a lot of them, especially the annoying ones like LinkedIn or similar. The notifications will still go through via the “mirror notifications” handsoff-style functionality at least.
And the lousy players like RunKeeper, I don’t use them anymore, their loss, I just use the native workout one now.
That would explain a lot of the craze that happens every single iOS update. If they would just point it out, something simple “your phone will reindex itself and rebuild all files/folders/etc, give it a couple of days for battery to be back to 100%”.
