I think the argument is a bit more vague than that, quote the article:
"And this is why Tim Cook is willing to go to the mattresses with the US department of justice over iOS security: if nobody trusts their iPhone, nobody will be willing to trust the next-generation Apple Bank [...]"
All the author is talking about is a general perception of trust, not any actual backdoor.
> I'm going to assume you know what Apple Pay is: you use your iPhone, iPad, or Watch as a trusted, authenticated identity token in a shop to pay for stuff. It ties into your bank account and basically your phone swallows your debit and credit card.
I thought that was fairly explicit. If the phone (or watch...) is going to be the primary tool of payment than its security is paramount. Apple wants at least the same level of protection against tampering as the chip inside a modern credit card.
"And this is why Tim Cook is willing to go to the mattresses with the US department of justice over iOS security: if nobody trusts their iPhone, nobody will be willing to trust the next-generation Apple Bank [...]"
All the author is talking about is a general perception of trust, not any actual backdoor.