Apple doesn't have to, and doesn't, follow the rules. Their apps frequently use private APIs, for example.

Wasn't it the mere allegation of doing that that got MS in legal hot water back in the day?

I mean it is Apples platform and they can crash and burn it as much as they want, it is just interesting.

It was far from "the mere allegation". It was a long history of doing so, over many years, combined with overt efforts to break the products of competitors, combined with owning virtually all of the market for PC operating systems.

Siri technically isn't an app

I guess not an 'app' as such, but it's still a program on the phone.