It seems the W3C is opposed to grassroots innovation from browser vendors without having every feature pass through their committees first. I don't buy the arguments about monopolization, and if most of your user base is on iOS or Android then it makes perfect business sense to prioritize those platforms when building out your design. Graceful degradation and progressive enhancement are widely recognised good practices, but by no means are they mandatory for the success of the 'Open Web'. The benefit Apple has brought by not bundling Flash with their iOS devices (suddenly that 'monopolization' doesn't look so bad, does it?) far outweighs any drawbacks caused by the implementation of non-standard features in WebKit.
In fact, you know what the real enemy of the 'Open Web' is? The use of terms like ‘de jure’. In the real Open Web, there's no room for central governance, and no tolerance of the assertion by any organization that they represent the sole font of truth.