Theoretical design is pretty worthless until you try it out. Until then it’s just an idea or hunch you have. You hope that your experience and intelligence will tip the scales in your favor but that’s all it is. And often your design still has flaws anyway because there’s bound to be unknowns. So then your hoping some kernels of ideas still hang on after encounter with the world and that the ideas are directionally resistant that you can keep the design going forward.

Design is useful as a tool to sketch out a plan but it can definitely become thinkism if you always hand off your design to someone else to action.

Also, the author is talking specifically about research type problems where there’s a lot of unknowns and the problem space is not well trodden and understood.

Also, I don’t know when the last time you built anything is, but talking with mechanical engineers and construction engineers, it’s all the same. You have your designs and then you open up a building to do repairs or start construction and some surprise presents you that you weren’t expecting. That’s what the research phase is for where they learn all they can about the problem space before they start designing (in this discussion ignoring all the years of trial and error that built a base of experience already) and even still in practice problems arise.