Nearly a year for a turn-around time from producing the myth to when it makes to air seems like a terribly long time. In fact, I'm fairly sure it's a lot shorter than that given other evidence we've seen of them doing production of a myth and when we see the episode. I guess for the cannonball myth they waited longer for things to settle down a bit given the mishap to make it a bit more in the "forgotten past." It was nice they addressed the issue up front and in the episode itself, though as Christopher said it also would have been nice for them to address how much of an absolute fluke this was.
Myths tested were all pretty interesting overall. I do wonder how the "SimDaver" would have survived the initial myth tests rather than the more rigid dummy. I also wonder why they didn't test the dummy in different falling positions. I can see all of the pelvis and spine damage coming from the fact that it was landing directly on those parts as opposed to trying to "land flat" to disperse the damage more, a "cannonball" type landing or something else. Landing directly on your ass, sure, makes sense you're going to mess up your pelvis and thus lumbar spine.