You seem to be saying "if stolen iPhones are worthless, iPhones will be stolen and become e-waste", but if stolen iPhones are worthless, very few people will steal iPhones.
There are, of course less anti-consumer options than requiring active first-party involvement in any parts replacement. One would be keeping a registry of stolen phones and having the OS phone home after detecting a new part. Of course, that would cost Apple a bit of money (I think they can afford it) and only work with a locked-down OS (not to my taste, but I see no signs of Apple changing it), but it serves the legitimate goal of disincentivizing iPhone theft without raising the barrier to repair and creating extra e-waste.