The Air Force didn't change their story. They amplified it. The balloon explanation made no effort to address the bodies, merely the debris (that is, the stuff that was really there). The "dummies" thing is in addition to the balloon thing. And as I say, it was silly. There's no need to "explain" the inventions of such as James Ragsdale and Glenn Dennis. There's not the slightest shred of evidence that their stories are true.
What we have with Roswell is the real story from 1947, which is high-reliability and low-strangeness, and the later stories from the 70s, which are high-strangeness and low-reliability. Saucer-peddlers like Stan Friedman and Kevin Randle grafted then together, hoping to get a high-strangeness, high-reliability event. It's a perfect example of why "UFOs" are not taken seriously, even when they might deserve to be.
Dismiss it if you will. I think that adding to a story is the same as changing it.
Either your research on the topic is spotty or sparse.
Your statements have been demonstrably proven otherwise by a number of solid researchers.