Earlier quoted context omitted.
Are you seriously suggesting that Robert A. Heinlein, former naval officer, wouldn't care about the distinction between a ship and a boat? And you still ignored the two most difficult ones.
I think he knows the difference, but surely meant the life skill of captaining something rather than the literal many-years-to-acquire technical skill of doing so, because the former makes sense and the latter doesn't. Which two? Designing a building I see I skipped. That seems pretty attainable, he obviously didn't mean 'be a trained architect and building engineer' like you interpreted it. People in charge of organ…
The task you are describing is not design; it’s specification or briefing at best. Heinlein was also an aeronautical engineer. Engineering is are also a profession where imprecise language costs lives.
The hardest one was “plan an invasion”, but I’m sure you’re about to tell me that a former naval officer and author of some of the most famous pieces of military science fiction didn’t really mean “plan an invasion” when he said it, or that despite modern history being full of poorly-planned invasions (and there’s one going on right now), actually it’s something you can learn on a three day course.