> designing systems where it's not possible for those negative incentives to exist
No doubt, but even in simple systems this is considerably more difficult than it sounds. Incentive systems are not easy, and any incentive system is often twisted into a game that produces unexpected poor behaviors. Try to achieve that at a 100+k employee company and you're guaranteed to end up with misaligned or counterintuitive incentives.
The reason something stronger than simple assertion matters here is because Apple actually has added an incentive system: trumpeting privacy as a core feature means they tie their brand to their ability to deliver on privacy. That means that being called out for privacy issues has greater potential harm for the company, and thus its bottom line, in a way that's far more direct and monetarily impactful than $100 annual developer fees ever will be.
Even cynically, you can see the same mechanic at work with the recent reduction of app store percentages for small businesses. Apple has made it a core part of its developer outreach that the app store is a good thing for developers: they've made it part of their brand. If they're called out for something that makes many of those developers disagree, or even for something that makes users perceive that part of the brand as incorrect, it has implications to the whole company's bottom line (not just the developer id sliver of it).
> it's useless to talk only about the intentions you can prove just by looking at their formal decision-making process
For what it's worth, my point isn't tied to formal decision-making, it's tied to the informal parts as well. What I'm saying is that this can be a completely technical decision that relies on the existing business structure without ever taking into account whether it will raise revenue from developer ids. The developer id's existence is a fact. The “DoS resistance” characteristics, if you will, of having the developer ids cost money is a fact. As a system architect, leveraging those facts for system security seems perfectly reasonable. Yes, absolutely they should have taken privacy into account as well. “We haven't used it” and “we won't use it” aren't the same as “we can't use it”.
But here's the thing: to me, the strongest indicator of whether a company is committed to an approach is whether they react positively when they are called out, or whether they double down on their mistakes. Apple was called out here, and they've committed to doing just about all of the things they should be doing. You could use this same framing to say that Apple isn't as committed to developers thriving on their platform as they are to living up to their privacy commitment, of course.
Tl;dr: customers are part of the incentive system, tying your brand to a commitment aggressively as Apple has tied theirs to privacy has an impact on customers, and this is a great way to introduce an additional external forcing function to your internal teams.