The reason that timing matters more than you might think is that it's timing. It's a lot like the foot fault thing in general. To get your foot correctly placed, or to make sure the disc leaves your hand before your foot leaves the ground, means that you have to split your focus between your line - the basket, and what your body is doing. When you remove all thought of your foot placement, then your throw is easier. How much? Well, if you're a rookie, a lot; if you're Paul McBeth, well, a whole lot less. If you're Ricky, apparently not at all since he doesn't appear to worry about it in any way, other then when making comedic videos. Lest someone cry Ricky bashing, the comments here run deep. Set Ricky aside, I admit his stature and presence on lead cards makes him an easy target. I've seen plenty, two mentioned right here, and many over the years.
It can be done correctly, many players do, but enough don't that it should be an issue.
As an aside, I was watching one of the talk podcasts and I saw the questioned raised, is Ricky footfaulting to gain an advantage? That's a lot like asking if someone was born rich to gain an advantage. The fact that someone is getting an advantage doesn't mean they planned it out. "Okay, I'm gonna foot fault to gain an advantage," is not the same thing as foot faulting cause you're not watching. The number of times a player consciously thought to foot fault or even had the thought, "I'm not gonna pay attention because it will get me an advantage," is pretty darned low.