I don't think so....
There was a recent thread on the VF forum answered by a reliable poster who is ACE (AFAA too I think) certified, and the answer was that the definition of high impact is that both feet come off the ground at the same time. Jumping jacks, plyos, etc. That's not the same as high intentsity, though, because that high aerobic intensity can be achieved with low impact moves as well.
An interesting point that's just starting to come out (this was on the VF forum too, just last night) is that high impact, in moderation, is NEEDED for healthy joints, apparantly it strengthens the surrounding tendons, ligaments and muscles. The tricky part is figuring out the right amount of high impact to do if your joints are vulnerable to overuse - I'm still trying to figure out this one myself.
I modify a lot of Cathe's tapes to low-impact, but it's easy to keep the intensity up. I save high impact for when the moves demand it, and to be honest, it's more fun, for me anyway.
Sophie