Not so sure I agree... I don't think they would have even considered developing ChromeOS if they hadn't somewhat proved the offline web concept with Google Gears and were expecting similar functionality to be rolled out in HTML5. Also, NaCL (or whatever the heck they call that) goes against the browser (which is all the user sees after all in ChromeOS) as being a complete dumb terminal.
To your point, the ChromeOS machines were really little more than dumb terminals when they rolled out, but I don't think it was the intent of the design and architecture to be completely useless when not connected.
As I understand it, Nothing here really breaks the model/architecture... everything is still synched to "the cloud", whatever local info that is stored on the machine is just cache, and the device is still, at heart, stateless. If you drop your ChromeOS Netbook in the lake (or it gets stolen, etc) at most all you lose - data wise - is whatever you had worked on since the last time you were online.
I can almost say that about my cellphone (no way to sync my txts/pics/videos/apps/etc to Exchange - but contacts, mail, and calendar no problem) but I definitely can't say that about my laptop... which to me, is the real, intended point of ChromeOS.
Just my $0.02... FWIW :)