But in the article you link to as [0] it also says Apple had already refused to comply with an All Writs Act request in an unrelated case several months previously. It doesn’t seem that the under seal request would have made any difference to their actual decision, which they’d already made. This pretty much kills dead any suggestion that they somehow changed their mind for PR reasons, in fact they pretty clearly didn’t want to publicise it hence the seal request.
Also the PR boost from this is far from free. Aside from the huge cost of engineering all this security into the system, to the point of delaying major new features by years in order to get the security architecture into place, its also costing them a chunk of the Chinese market. The Chinese government is absolutely not happy with this sort of consumer privacy stance and has been cracking down on security services and features on the iOS platform. They’ve banned VPN software and features, banned communications apps, even screwing with Apple by barring the iTunes media business, and stalling Apple Pay.
Going up against the US government arguably does Apple no harm, but setting themselves directly at odds with core Chinese government political goals such as pervasive monitoring and censorship of all forms of communications is going to be a real battle.
If they just wanted a marketing advantage, they’d just build in some anti add-tracking features and be done. Security and privacy is so appallingly bad on Android even a perfunctory effort there would put them miles ahead at little cost. The extreme lengths they’re going to goes way beyond anything remotely necessary for a marketing advantage.
Finally, Apples stance on accessibility shows just how serious they are about serving their users. The cost of their accessibility efforts must be dramatically higher than any possible financial or marketing benefit and they’ve been doing it for decades across platforms to little or no fanfare.