On that topic, I just took a quick look through that site, having not done so for quite a while, and saw a pretty glaring error, or at least something likely to be confusing to newbies.
On the "Joystick Engagements and Restrictors" page where it shows the diagram for 4-way, it shows a pretty large crossover for diagonals, which isn't necessarily true. The amount of crossover is dictated by the size of the restrictor and/or the size of the dead-zone. The page seems to imply that the ideal 4-way restriction is a "plus" restrictor, which may be true in theory, but in practice it is almost never used and if done poorly, would be likely to be universally detested by users. As I found when designing the 4-way restriction for the Dominux sticks, even when done as well as possible, users ultimately preferred the "diamond" shaped restriction. Further, well-designed switchable sticks mitigate large crossovers in the 4-way orientation by finding a "happy medium" between that and the 8-way orientation, which is why they are not without some compromises in each of their respective modes. So even considering an optimal 8-way with a rotated restrictor for 4-way operation, isn't really the correct way to think about things, as it would not implemented in a such a simplistic manner.
It also tends to gloss over the effects that size and shape of the actuator will have on any of those actuation zones diagrams. And I won't even get started on the 49-way portrayal.
There is a lot of good info on those pages, but as with anything, it's probably a good idea to do a little critical thinking when viewing them.