That's why Apple gives the consumer an authorization code that they can use when re-selling their phone, to unlock its parts and permit their re-use. Since thieves don't get that code, it protects phones against theft and allows re-use.
Because if they didn't do that, anti-theft would be just a useful excuse to further rob the consumer of agency.
They do give out such a code, right? I'm just assuming here, but since they paint themselves as such champions of ecology [1], they must. Because if they didn't, that would make them hypocrites, and liars, in claiming there is no way to deter theft without taking rights from the consumer. And we know Apple is honest and on the consumer's side, so that can't be it.