Not sure if you are replying to me, but if you are, then, I am particularly interested to understand why with a new battery the OP won’t get the presumably original use of 11 hours?Simple math. My iPad Pro was at 87% getting up to 7 hrs. Now I got a new one. Gets like 8 hrs.
That’s because you upgrade the running iOS.
You’ll have reduced hours even with a brand new device if it isn’t runn8ng the first iOS that generation of device shipped with.
Is this the reason why? You have evidence of this?