Okay, after spending a month or so playing around with Speaker Workshop and building a test jig for that, I now understand this thread a lot better.
SW uses MLS signals and FFTs to measure impedance by the same method: Line Out--> Amp --> Speaker --> Line In.
Seems this is the same, except using the burst sweep tones. Very cool.
Some things to remember if you all are going to try this: check your output voltages carefully! BEFORE YOU PLUG INTO LINE-IN!!! I always make sure the levels are set at less than 1V before plugging in. My jig has a 16:1 voltage divider built in, so that's not a problem, usually.
I'm using an M-Audio MobilePre, which is nice because I can easily go from impedance measurements (where the input signal is a reading across the speaker terminals) to sound measurements (ECM8000 mic swapped in for one of the channels directly to the MobilePre).
Next time I set the rig up for testing, I'll fire off some impedance tests with REW and compare them to the SW and manuf. specs. Always nice to have another tool in the toolbox, especially one that's already loaded on the computer!
