“I wrote FAT on an airplane, for heaven's sake”

I think the real lesson here is that every time you add a feature, you are adding development overhead to every other feature, leading to exponential development time. I'm sure if segment tuning was one of the first thing to go into windows, it would have been much simpler to implement. However, at later stages in the development you have to account for how different, already-written applications are loading their memory, and thus the feature needs handle far more edge cases than it would have if this was an earlier-implemented feature. I'm not saying the overall time to develop segment-tuning would be shorter, in the long run had it been developed first, but the perception of development-time for this feature would be shorter (since any segment tuning edge cases that you ran into while writing an application would be considered part of the app's development time, not segment-tuning's development time).

I'm sure that if Mr. Gates had implemented FAT at a later date, he would have needed a much longer plane ride.

Or pen or paper

read the article after you finish reading the headline.

If he'd kept one foot in the codebase - he might not have made so much money - but his software legacy might have turned out differently.

Another possible conclusion from your analysis is that a proper architectural separation of concerns (which could allow one to bang out code like he's still on that plane) has not been practiced in Windows, and by the time Bill was offered the opportunity to code something in Windows it was already hopelessly entangled.