Completely missing the point.
First, it's not an issue of consumers being able to buy platforms elsewhere -- this behaviour is disliked because it's anti-developer (multiplying the workload to create a cross-platform application) and anti-competitive (removing some, or all, developers from being able to effectively work on more than a single platform -- Apple's platform), not because of anything directly to do with consumers or consumer choice (only indirectly through the anti-competitive edge).
It's also not necessary to maintain quality. That's a bald-faced lie on Apple's part (and someone formerly in such a position should know better than to take something like that at face value), as they already have stringent requirements on accepting applications (including quality requirements, which are all-too-often disregarded even with 'natively-coded' applications to have quality used as any sort of justification), and due to the ease of creating low-quality applications no matter what tools are used. Quality cannot be measured by choice of programming language.
It may be anti-developer, but it's pro-consumer.
Flash content, as it stands, is not optimised for the bandwidth restrictions of mobile devices. It's not optimised for a touch-only environment - many a Flash developer exploits mouse states and keyboard interaction. Even though the vector graphics mean Flash *should* scale, developers do not generally create resolution-independent Flash files, they expect their designs to display at set dimensions.
If Apple just flicked the switch on Flash, users would be exposed to a ton of content that eats up their bandwidth, slows their phone to a crawl, and is utterly unusable in every respect.
So that rules out effort-free web content; and simply republishing that web content to iPhone using the CS5 functionality will only solve the bandwidth problem. The interface is still ill-suited to the device.
If a developer is creating something up front in the knowledge that it will be published to multiple devices, sure, they will potentially make smart decisions to avoid those issues, but they're still going to spend less time polishing their app specifically for iPhone users.
Unlike web content and Android, the iPhone ecosystem is a proven money spinner. The success stories roll in every day about folks who get into it as a hobby then end up making a ton of money. If a developer wants to get in on that gold rush, they should be expected - and required - to create a polished experience for the device. Using Flash Professional and exporting to multiple formats is not going to result in a polished experience. If you think the app store is full of crapware now, it would be far worse if Apple opened the floodgates.
I'm a developer, and sure, I would love for my job to be as easy as possible. I would love a magic button that allows me to create something once and hit a button to create a polished, targeted version of my work on Windows Phone, Android, iPhone OS, WebOS, the Internet and high tech toaster ovens. It ain't going to happen... unless I use the holy trinity of HTML, CSS and JS. Apple aren't restricting those at all, by the way.