Apple Maps has been able to display full-size navigation on the lockscreen since iOS 7 or 8 (?). Apple Maps also has access to a special style of notification that no other navigation app has.

iOS 7 was released in 2013. 13 years ago, aeons in tech land.

So "APIs are hard to get right the first time. I could see why they wouldn't want to release one until they've dogfooded and refined it." is crap. They're hoarding private API access purely for competitive advantage in services.