The disastrous thing is that it would be less useful to have a maximized window be 10x the size of its contents. For example, IMO the behavior of safari on maximize is just beautiful, because it's tailored to the specific website you're viewing.
If the application is a window into your data, why make that window bigger than necessary, thus obscuring your desktop, or some other window behind it? That may not be disastrous, but I think its intent makes sense.
Without further explanation, I end up suspecting that when he writes: "it almost never does what you’d want or expect it to," the emphasis is on his expectations as a Windows user, not on what he would prefer, all things being equal.
[and for the record, I'm speaking as an Ubuntu user, who has never owned a mac]