Why is that absurd? Because the plane was not transported by truck or train it was bad?
The Germans where doing the same thing because of all the bombing.They pretty much turned their aircraft into a cottage industry and spread production everywhere.That is actually very clever it makes bombing you enemies production facilities impossible.My grand father saw many of these German underground and forest factories they where just as good as an American factory only smaller and spread out.
The Japanese began doing the same thing towards the end of the war.
I am not saying that the Zero was the best plane of the war but you are underrating it somewhat.If a plane inspires another nation to make a plane(or planes) that is better that is the sign of a good plane.Not sure why pilots where so happy to get either F6Fs or F4Us if the F4F was a better plane than the Zero overall but they where pilots maybe they did not know what they wanted.
And by your statement that makes the F4U a bad plane as well because it was not the most agile aircraft.Every plane is a design compromise in some way.You cant that one is bad for this reason but not another.
The Zero was a design compromise that they failed to improve in a timely manner when it was clear that opposing aircraft where getting better than it was as the war progressed.