That's a catch 22, and none of it has to do with user experience.

- It's not easy because they have a historically web-centric organization.

- They have a web-centric organization because they had not invested in building a broader engineering team.

- They did not invest in building a broader engineering team because they have a web-centric organization, so they stuck with web technologies.

Their engineering management put appeasement of their existing web-centric engineering organization ahead of user-experience.

User experience is the not the only governing factor in software development. As the John Carmack post on HN front page says, software engineering is a social activity, which as you can imagine has more than one goal factor influencing it. I don't know what politics went on in this decision, but choosing a HTML/JS platform on mobile phones on definitely has its technical advantages. Though it doesn't apply to Facebook, a financial advantage would be to save money on hiring iOS experts/programmers.

As you noted, the financial advantage does not apply to Facebook. Contrarily, there's a financial advantage to shipping a better product, if you can afford to do so.

I'm interested in your supporting argument for other governing factors or software as a social activity, and how that relates to making engineering choices that sacrifice product quality for some notion of engineering perfectionism.

A better product does not have to be on the native platform. There is financial risk involved in hiring a iOS/Android professional.

Are you stating that contrary to Facebook's experience, web applications provide a superior user experience on mobile devices?

No, he isn't. Another way that a UIWebView can provide a super experience to custom NSViews is if the UIWebViews implement more of Facebook's functionality than the custom views, or if the features the UIWebView expose match the ones users want better.

So if:

- Facebook fails to deliver features through the superior approach ...

- ... but does deliver them through a lesser approach ...

.. then the mechanism they use to deliver the features provides a better user experience, because it has the features, thus justifying the choice to deliver them in the through a subpar mechanism?

That's ... circular. Painfully so.

It would be better for the user experience if they delivered features with the highest level of quality they're capable of providing, and that's demonstrably not inside of a UIWebView.