Seems it's more about focusing effort on standards evolution versus de facto standards. That said, certainly the latter informs the former.
Excluding the nefarious, it's not a bad idea to hide webkit-specific prefixes, bundling up nonstandard extensions to the standard in a single about: configuration. That said, one has to assume that this is the webkit variant where Google will focus all of its engineering attention. It will then compete against all other variants. After a while, what will webkit mean?
Will be interesting to watch and should add more vigor to the competition.