One thing that surprised me was the way they said they were going from mild steel to chromoly. So... it wasn't already chromoly?! I always thought they'd been using chromoly since the '70s. In fact, looking back, it looks like the '79 test says it's chromoly, and that's also the '78 frame. I imagine the very similar frames of '76/77 were also, but I don't have a bike test to prove that.
Either way, it appears that they went to chromoly, then mild steel, and now back to chromoly again. Was there a reason for this, like cost or maybe a supply issue?