I can see how the tibia/femur ratio can make sense. Thinking about it a bit more.... I think squat strength is a big inflencing factor, as when you look at most any football player, they get down pretty deep as well. That cam wake 11'8 jump is a good example too. Then again, I remember watching staffan strand do some standing high jumps, and he dug down unbelievably far, especially for a high jumper with a bad squat.
I have long tibia length compared to my femur, but I can't squat for sh#t (not being able to hit 2.0x when you have been lifting for 13 years is kind of weak), and I have less knee bend than anyone I know on my standing vertical. A lot of this though is because I get a lot of power out of my upper body, and my legs play a slightly more reactive function than most. I suppose there are a lot of factors, I would like to see more research on it.
I bet achilles length and structure has something to do with it as well, a great study in the JSCR came out a few months ago talking about how athletes with differently structured muscle-tendon complexes in their calves produced force differently in standing and running verticals. Long tendons were good for standing vertical jumps, and short were not good. Case in point I had a swedish long jumper who went 22' this past year and wasn't that fast either, who only had a 25" standing vertical. His achilles were really short.... and so are Stefan Holm's for that matter, and his standing vertical is like... half of his running. KB wrote about that in one of his recent articles too.
I would be really interested if more research came out on the knee bend topic as well.