If you ever had to support "Dumb Terminals" from an IT standpoint, it was certainly easier the dealing with Fat Clients. The Chromebook Architecture takes the best of being nearly stateless and makes managing devices much simpler for IT. Someone else in the thread said it earlier, this article is more about archtecture than Chromebooks.
So the underlying archtecture is similar, but make no mistake, these are not connected to main frames in the cloud and their ability to run cloud apps that are able to compete with fat client installs of MS Office is light years ahead of any dumb terminal.