Sorry to hear about that working Hummer and but am glad to hear you are getting your money back.....but
In the engineering field there are always revisions made. I make them, the company I worked for before did the same, they all do. If I design a part and give it a part number for remanufacturing a die cast machine it may work perfect on "that model year" machine we are working on but when the OEM makes a change to their next model year and my part won't fit then I may have to say add a extra hole so it will fit the newer and older machines both hence why it will have the same part number but have the revision letter on my print/part also. Hell, I have seen drawings with revisions up to the letter "T"
Not trying to make a excuses for Hypertech but just to explain that we all do it and sorry that you got caught up in the "revision game" from one year to another and that it just happened to be that their revision added the HUMMER programming to their programmer later.
Edit for spelling, 5:00 AM sucks to be trying to post
Later, Easy Ed