Turns out it's impossible to prove what state those water tabs were in before the device was opened by a technitian in the back room ;)

Which also change colour due to humidity changes.

… which is water.

It’s actually impressive how resilient phones are.

True, but regular water rarely harms circuit boards for a one time exposure. Salt water, or soda, on the other hand... What Apple really needs is a USBC taste tester :)

Maybe they could use some kind of "corrosion canary"... some piece of metal that will behave like the circuit components in a standard way.