We have a recurring situation where all vendors (save for Apple) show interest in standard, but because Apple does not express that same interest, the standard gets waylaid.
That is literally not true – Google, by some metrics the biggest vendor, has also shown no interest in PE.
Frankly, I don't see that much of a problem with Webkit and its' adherence to standards. Broadly speaking, it adopts new features and standards somewhat later than FF and Chrome, primarily I expect because of the slower release cycle, but it does seem to eventually come on-board.