They touch on that in the link. "“There are regulatory and commercial and moral reasons for privacy from all sectors,” he says. To give a commercial example: Apple wouldn’t want Samsung to be able to track its transactions and gain valuable competitive intelligence."
Not at all surprising that Apple is trying to vertically integrate as much as possible. If it were cost efficient to do so, I imagine Apple would love to actually produce their own chips (though given how much scale is needed, I they are definitely a long way off from that).
I agree with this sentiment.