Further Insight Into Leg Cramps?

So, I've just finished Again To Carthage, the follow up to Once A Runner. No book review today, just this:

In both books you can find some pretty solid training advice and useful day-to-day info.

In Carthage, there's an interesting tidbit about getting leg cramps in a marathon, but not during training. I have often been baffled by this, as I've never once gotten a leg cramp in a training run, but I have experienced them in the race. What's up with that? To date, the best answer I've gotten is from the Sports Scientists, who relate it to misfiring of the golgi tendon, among other things. Here's another view, from Again To Carthage:

He remembered Denton's lecture: "In the marathon, you can get cramps at almost any time. They're not like the ones we used to get towards the end of hot-weather workouts, not based on electrolyte depletion. I got them halfway through my 2:15 when I picked up the pace suddenly. They're usually in the hamstrings, sometimes the calves or quads. You're just over your anaerobic threshhold, but just barely. You start generating ketones from burning fat without enough oxygen, the ketones start
circulating , confusing your synapses, causing them to misfire. You cramp. Joe Vigil laid it out for me. The thing is not to panic. They feel pretty bad for a while, and you may think you're done for, but they'll go away if you back off for a bit and run them out."

The science nerd in me loves knowing...why. However, given the information above is from a fictional novel about running, not sure how solid it is:)

[ORN: Obligatory Running Note] 6 miles in 58:40. Little faster than my base pace runs usually are. But I felt really good today. It seemed like I was experiencing the unexplained fitness boost I always feel after a race. Perhaps I should have reined it in with a key workout tomorrow, but I'm still flying high from the race experience...