That’s down to a manufacturer to prove to the consumer if a product has been abused ...
I'm no expert in law (in any country) but are you sure that's how the European law in question is written? I would have assumed that it's actually a matter for the manufacturer to prove to
a court or some other regulatory body, when such things are in dispute... not to the consumer.
A battery on an iPhone should not be depleting within 2 years to an unacceptable level (-80%).
I entirely agree -- and under ordinary circumstances, they
don't deplete that quickly. Same is true of pretty much any Android, actually, because it's more a matter of physics than anything else. The batteries in Android phones and iPhones aren't all that different -- but the fact is, batteries eventually wear down. Mind you, modern cell phone batteries are a fairly well established industry, so they don't
usually wear down to below 80% within such a short time span, unless there is unusual wear and tear or a defect.
But quite frankly, a lot of people don't really comprehend what constitutes unusual wear and tear, and so almost all users who routinely abuse their electronic devices are going to be prone to claiming it was a defect when the device ultimately fails. It is my opinion that codifying a three-year warranty accomplishes two things: 1) it
encourages users to ignore best practices and freely abuse their devices, and 2) it forces manufacturers to increase the price of those devices, in order to accommodate a very realistic expectation of a higher number of warranty repair claims. (Feel free to double check me on this, if you like... but a
two second Google search suggests that the premium in Europe may indeed be as much as ~30%.)
My old iPhone X (which my daughter inherited from me when I upgraded to a 12) presently shows that it is at 73% of its original life. The only reason I know this is that she
only just started complaining that it was draining too fast. That iPhone X is the one and only time that I have ever pre-ordered an Apple device for day 1 delivery... so it is nearly
5 1/2 years old. While this is of course anecdotal, I mention it to illustrate that it is perfectly plausible for an iPhone to live a useful life
well beyond that 2 year timeframe that you mention. And I would suggest that such long life expectancies are quite common... at least, for people who do not routinely abuse their devices.