He also talks about Rounding, Balancing and Complexifying.
Complexifying means ensuring there are at least 12 viable approaches to every problem. Rounding and Balancing means ensuring that none of those 12 stand out as the obvious or optimal one, so the PCs are free to pick any one of them, or even a 13th that I didn't think of.
The goal here is rich tactical complexity. If there's one obviously optimal approach, they're going to pick that one. If there's two, they just have to decide between those two. But if there's a dozen, and none of them stand out, they have the freedom to create their own solution instead of just following whatever I thought of.
And that, I think, might be the core goal of HTT: giving the characters (not the players!) the freedom to create. To create their own solutions, their own plans. Which could be anything.
Let me know if any of this rambling makes sense. I'm talking more about S. John Ross's ideas about HTT adventure design than about my own campaign here. Is it interesting that I share that process and my thoughts about it? Or should I just focus on the campaign itself and keep the rest private?