Apple consumers have been insulated from the semiconductor industry practice of binning for years by high margins and insane growth. Basically Apple could afford to throw out the "only 9 cores work" chips (or whatever) instead of selling them as separate products or performance tiers (or whatever). But now the unit growth is levelling off, so they need to squeeze for "growth" by expanding profits instead.

And one way you do that is by selling the extra chips you'd previously been flagging as yield failures.