Ok, so I thought I'd at least check this out myself to see if there was any validity to it.
Go into Phone Information, press MENU, and tap "select radio band." You should experience a Force Close, don't panic, this was supposed to happen. Scrolling down shows that the preferred network type is GSM auto (prl).
Followed the instructions in the first post.
First observation: I can scroll right down to the radio band pop-up menu without first having to press Menu...and it's already set to CDMA auto (prl).
When I do press the menu button and then the select radio band button - that does cause a force quit. Upon the test menu coming back up, the radio band is then set to GSM auto (prl). But I'm thinking this is due to the force quit itself (a bug? or perhaps the proper behavior because there are really no 'choices' of radios available?).
So I went ahead and reset it to CDMA auto - then rebooted. Checked it again, and it remains at CDMA auto.
Out of curiosity, I then did the process again, including forcing quit, but this time leaving it at GSM auto and then rebooting to see if it auto reset to CDMA. When I checked it, it was still on GSM auto...so I switched it back to CDMA and rebooted. It's still on CDMA auto now...which is where I started.
So...I suggest that GSM auto is the DEFAULT setting for the phone for some reason. Could they have come from the factory this way? Possibly. Could some app/process on your phone or factory reset cause this setting to default? Quite possibly. If you open the test menu and scroll down WITHOUT pressing the menu button (and force quitting) and it already says CDMA auto, then you've likely been alright all along.
That's my $.02