The purpose was to clarify that the obstacles to constructing modern nuclear weapons is not accurately characterized as "99%" fuel-related. Even if a group were to obtain a stockpile of ready HEU and plutonium-239, there is knowledge they simply will not have because they did not spend a trillion USD testing different bomb configurations last century. The difference in yield is two orders of magnitude.
Aka this has zero relevance to the proliferation discussion. Anyone having the problem you are describing long ago already created a basic nuclear stockpile.
Notably, neither China nor Russia seemed to have issues creating Thermonuclear weapons despite the shortcomings you identified either.
