If you have a majority of apps dependent on a third-party framework then Apple is no longer free to update/innovate without consulting and likely being slowed down by that third party. It also means that Apple would have to work closer with that third party.

On the desktop, Apple doesn't really give a damn about an update breaking flash in your browser. But they do have to do a lot of regression testing against a lot of popular software. The argument is that perhaps they'd like this process streamlined on the iPhone.

It's sensible, but I still think it's more about not letting the platform become the commodity as both Mark and I have said before.