I agree 100%. Below is the E-Bay Item, they have pictures of the USB port on the side of the 576. I believe this is the same product that you are talking about. I may not be the sharpest knife in the drawer, but the evidence is overwhelming that they are definitely picking off that switch data from somewhere inside the instrument.
Look for E-Bay Item #302445112576. You can also search for “576 Tektronix” as the search term. You will find it listed at $4500 plus $195 shipping. Supposedly a “refurbished and calibrated” 576 with the USB port and software.
When you find it and have a chance to look it over, I would like to hear your thoughts.