>So you would want to know if the phone was blessed by an apple genius when you buy/sell ?
Very much so, I don't want my phone catching fire in my pocket or while charging, or people with little technical knowledge being scammed.
Would you want to know if the home you were buying was wired by a licensed electrician, designed by a licensed engineer, etc?
No, not really. I'd want it inspected, of course, but that's about it. Same with buying used cars. If the house wiring or my used car fucks ups, I'm safe in the knowledge that I can just hire someone to fix it for a reasonable price, and I can be reasonably confident that they'll do a decent job because the knowledge and the parts to fix it are freely available to anyone.
>designed by a licensed engineer, etc?
Maybe, but then designing a product is different than repairing an already designed product. We also have regulations for that kind of thing, so even if I have no idea who designed the house, I can be fairly confident that it's going to be fine because the house was built in the first place, and as before, I can also have it inspected and repaired if something is wrong.
Nothing of this is new, people have been going through the same shit for a couple of centuries now, we went through it with cars and appliances earlier in the last century. Don't let Apple and other electronic manufactures convince you that they're somehow special or different. It's not arcane magic and these problems are not unsolvable. They're just not willing to solve them in a way that's not user-hostile because they have not real incentive to do so.
Also, a fun fact: an iPhone XR replacement battery is $80USD from iFixit (the only vendor I'd trust) vs $69 for out-of-warranty replacement from Apple themselves, labor included.
Also, good luck finding an Apple store or getting your battery replaced in reasonable time anywhere outside the major cities, and especially anywhere outside the US.
That's to prevent people from
taking old batteries and
modifying them to appear new.
But the phone is old. That is known. You are buying/selling an old phone which has old parts. Whether the old part was genius blessed or not is of little concern as long as it is a genuine part. It is common knowledge that batteries age and that is implied when you buy an old device. If you are unhappy with that, ask for user replaceable batteries, not more DRM in batteries. I don't get this warped logic at all. Some amount of risk is assumed whenever you buy anything used. That's just life.
How do you know it's a genuine part? Maybe even the seller truly believes it is a genuine battery, but counterfeits getting into a supply chain is common unless very tightly controlled.