I think you missed the point in both cases.
The first link was not to show which components to use but rather the best geometry for success.
In the second instance, the stiffness, which you want loads of, was measured after the build, as you say, but that gives us the benefit of looking at the designs to see why those figures turned out as they were.
So now we can either use or avoid those ideas in our own designs.
Somewhere in this forum is a spreadsheet that calculates various gantry designs, you should find that and test your own ideas out with it.