iPad battery replacement

I have searched, and any threads about battery replacement seem to be more than 1 year old - so forgive if this is old news - just wanted to share recent experience.

iPad Pro Gen 1 12.9 - owned since new - original battery - no damage. Purchased 2016.

Only getting 2 hours 30 or so with just browsing and email use. To be expected I guess, no surprises.

Apple Genius appointment - diagnostics check - all okay in general - battery at 82% of original capacity.

I quite understand that since it's well out of warranty, battery replacement is my cost - no problem.

'Since battery is at 82%, we can't replace it - it needs to be below 80%, ie 79% or less - then we can do the replacement at your cost'.

Hmmm.

Go home and do my own tests.

Coconut Battery - 71.7%

iMazing - 73.3%

Tech Tool Pro 14 - 73.4%

More than 1 hour on the phone to (very obliging) Apple Support people - escalated 3 levels.

My question - how come all three of these apps give consistent results in the vicinity of 74% - but the Apple Diagnostics tool says 82%? .... of original capacity in all cases.

Answer - 'We place no weight on 3rd party apps. The Apple diagnostics tool is designed by Apple, for Apple devices. The less than 80% figure is not negotiable'.

So, there you go. I still have no idea why the Apple figure is significantly higher - though, to be cynical, it probably suits them.

BTW - even if my result had been 79% or lower - just for interest, they don't actually replace the battery in your device - they take yours, and give you a 'remanufactured' device of same specs - with warranty.

All very interesting.

Thoughts? .... other than, isn't it time you bought a new iPad etc etc ....