Well, I think you are just lucky somehow that you got one of the early test Kindles, which for some reason have the test mode scripts enabled. I have tested with a U.S. WiFi K3, and the ~usbNetwork appears to produce absolutely no result, nor does the ~exec command. The Kindle accepts these commands and nothing happens. So, unless you know how to enable the test mode on the Kindle, your method of initiating a connect probably doesn't work for the regular case.
Maybe some important piece is missing from ecostin's instructions, but thus far I wonder if anyone can confirm a working ~exec command?