Agreed, bodybuilders are hypertrophic masters.
I never said that there would be an even split or that both low and high volume methods would be used in a cycle, or that they wouldn't. In the end, your neural efficiency is the biggest enemy to future hypertrophy, which is why guys like Poliquin will tell you to do whatever it is that you haven't done before, and after 4-6 sessions of the same stimulus you will need to switch to something as different as possible to continue maximizing hypertrophy.
Unfortunately I can not currently delve into the functional mass issue. There is simply too much that is not publicly known there.
I am not arguing that the whole 75% thing isn't worthwhile or that it won't add more mass than a traditional high intensity, low rep program, but the how and the why is the great unknown amongst practitioners. Those details allow you to dissect what is happening in the body and learn how to take advantage of those processes with all different loads. I am looking forward to the day when I will be able to share that with you guys, because it will allow everyone to accelerate their gains.
There's a lot of good basic knowledge in your posts, and I like that you are sharing it here. Please continue!
One last comment: The higher reps work well for the olympic guys because they do not usually work in that range. It is a different stimulus and has vastly different demands on the internal muscle structures than what they usually perform. The simple fact that it is a different demand than their body is used to is one of the primary reasons they are able to gain mass so quickly with this training.
You may be interested to know that bodybuilders occasionally have to go very very heavy with low reps to break plateaus in size, for the same reason. It is not what their bodies are used to so they adapt more strongly to the stimulus.