Some of them are, some arent.. the mdl folks have found plenty of each
why didnt they talk about .net/sl/xaml eariler? who knows, but presumably because to they wanted to suck upp tp html devs.. there was a whole lot of other stuff they didnt show in that first win8 preview as well
build did show that xaml applications are a first class member in win8 and the leaks show this as well.
if you think they just put in .net support as an after thought you really havent been paying attention.. hmtl+js is just another application model, its not the application model.. just look at the sessions, they are pretty evenly devided among the diffrent models