This is an interesting point. Apple is pretty hard nosed on their predictions and capacity reservations, to the point where they could be funding part of this expansion at TSMC (as they have done for Hon Hai, among others, for decades).
I continue to be astonished by Apple’s ability to manage their supply chain so tightly (which requires not just an iron fist but very very intense internal process). They seem to be the only ones who can manage to do that.
And it’s not like other big companies are lazy; the part that really amazes me is that their process hasn’t leached out to other companies, as so much else does in the Valley.