But then Apple is not only putting themselves at a disadvantage against other platforms for long stretches of time (“iOS can do that with Apple stuff” is better than “iOS can’t do that”), but also giving up their ability to dogfood new APIs and test them in a much larger capacity than even a public beta would allow.

In order to remain competitive, they’d be forced to release half-baked/under-tested APIs, which is never good. That’s exactly how the Android developer story got as bad as it did at its lowest points.