Actually having just tested, I have a bunch of "aftermarket" lightning cables, and a few of them some of my iPads (I think the more recent ones) and most of my iPhones refuse to charge. Like at all.

So not fast charging, charging at all. They work on some of the iPads, so they do work.

Why do the phones refuse to charge then? Not fast charging, which I can sort of understand, charging at all.