"Ignoring Zones altogether"
I agree with both halves of what David was saying or implying.
Gardeners SHOULD ignore conventional wisdom at least some of the time - that's the only way we progress or at least disprove popular misconceptions. (If you might lose the farm with one mistake, following conventional wisdom might be more wise.)
But ignoring "what everyone says" is not the same as being ignorant of it. If you're trying to break new ground, it helps to know that there might be alligators in that swamp.
How can you ignore or defy the alleged facts effectively if you don't know what they are? If "everyone thinks something", there is probably SOME reason for it. And fore-warned is fore-armed.
(I don't know why having fore-arms is so important, but I guess it is. They do keep your gloves off your elbows.)