(Learning to dream lucidly is largely a matter of giving this a high probability and keeping it in mind, and updating on it when you encounter, for instance, people asking whether you're dreaming.)

I find this statement curious. Perhaps my memory is simply biased on the matter but every dream I can recall -- or, rather, every dream I recall recalling (and those are far and few between at that) -- has always been lucid. Even growing up this was the case. I've always had bouts of insomnia as well. I cannot discount the possibility that I'm simply recalling those things that conform to the patterns of my expectations, but I do know for a fact that I never had to "learn" how to dream lucidly. I recall one particularly vivid string of dreams I had as a child -- or, rather, one particular recurring facet of said dreams -- that all involved me being able to walk two inches off the ground. This is actually one of my earliest memories (I recall little about my early childhood). This "walking off the ground" was something I did because I knew it was a dream.

I have no inclination towards guessing the significance (or magnitude of that significance) of this.