I was pretty surprised to see it too! As I said in one of those posts, exercising options is viewed differently than open market purchases or sales for these purposes. This is especially true when cash is used to cover the exercise price and taxes and the shares are held in full following exercise, as Elon has done. I'm guessing that's how they got comfortable.
i will also stress that there aren't hard and fast rules here, it's a judgment call. Oddly, some companies tend to give CEOs more leeway in this regard because the view is "well, when DOESNT a CEO have material non public info about the stock of the company he runs?" If you applied that rule strictly then top management could never trade in the stock.