Ok, so I have been going crazy the past several months trying to verify why my ip6 drains battery during sleep and my wife's near identical ip6 does not.
We got her a new ip7+ and I have her ip6 now. All I can say is WOW. Something in my old phone must have broken or something. This new-to-me ip6 is sweet. I had reset it, and even installed beta 1 of 10.3.3 so I could use my backup to restore from.
This is how my old ip6 should have been working all along since it started battery draining after ios 10 came out.
Now I am of the opinion that there is some sort of odd hardware failure that prevents the sleep mode from FULLY engaging allowing the phone to think the screen is on, or something, when the rest of the phone thinks it is in sleep mode.