Yes, they tested on the HD2 and didnt release WP7 for it. But that was just one model, and it wasnt being touted as a "Hero" device by a major US carrier, a European device maker trying to claw their way back to relevancy and a software maker that has seen its mobile presence wiped out in a few short years. The HD2 had the internal hardware to run WP7 but as they said, it would have been a Frankenstien experience compared to current devices that are now instantly recognisable as running WP.
The major difference today however is that we're not just talking about one device model, but several; the Lumia 610, 710, 800, 900, HTC Titan 1, Titan II and Radar 4G, and Samsung Focus S and Focus Flash. These are all current devices and in some cases will be less than 6 months old in some markets. Saying all these new phones are obsolete and people should dump them and buy new devices so soon to get new OS features is ridiculous; but not unprecedented. This is how it is in some cases with some android devices.
The question though is, can Microsoft afford to do this with the state WP is in now? I personally think not, however they may think differently and will act accordingly. One thing though is clear to everyone, even the most stupid WP team member; a lot of people will be ticked off and will swear off WP, and just as importantly the tech press, which is seemingly frantically hoping WP will fail, will seize on this and absolutely destroy Microsoft with negative coverage, aided and abetted by the scores of android fanboys.
It will make the Kin disaster seem like a walk on the beach.