> What does the app being written in HTML5 have to do with Google changing the API?

Everything. As I explained above, please reread.

> The app would still have to be updated when the API changes.

With an HTML5 API, the API can be stable and still support many new features, video formats, ad formats, etc without change. NOT SO if you don't let google have their iframe.

> Additionally, if that were a concern of Google's, why aren't their apps written in HTML5?

Because they can update their own apps whenever they want to, but they cannot force Microsoft to.

>Because they can update their own apps whenever they want to

No they can't. Not on the phones, where it matters.

Yes, they can; they can have the older app say "you need to upgrade your app" (likely with a 60 or 90 day grace period), and put the new one on the play store. Alternatively, maybe their native client already falls back on an HTML5 alternative on a cue from their server - I have no idea.

What is clear from this debacle, though, is that Microsoft was unable to write their app according to Google's guidelines, and then took 3 months and still couldn't fix it - which means that Google definitely cannot expect them to upgrade to newer APIs ever - so it doesn't seem onerous to require them to actually use the official API now.