I don't know about exhaling from "up in the throat." From what you describe it sounds like you're talking about people who are concentrating specifically on making the sound you describe, not on the sharp exhalation of the breath form the abdomen. In that case, I would say no there is no benefit of which I am aware.
The ITF teaches one to exhale from the abdomen while executing a technique. While there can be conversations about how one is to breath when dealing with "consecutive" or "connecting" motions that can get a bit too focused on the minutiae of things IMNSHO the general rule is to perform a sharp exhaling of the breath at the moment of impact (indeed, you exhale sharply throughout the technique and at the moment of impact the breath is stopped) while at the same time tensing the abdomen. Much like the sharp exhalation you hear with weight lifters or tennis players, this is done to get more power out of the body.
Conversely, inhaling should be done through the nose, slowly filling the abdomen (well, the lungs, really of course, but with the movement of the abdomen used to facilitate getting more air into the body).
Breathing in this way should accomplish several things: increasing one's stamina since they are not out of breath, increase their speed since the body isn't unnaturally tight when actually moving, increasing one's power since the body is tightened at the moment of impact with the opponent and condition one to be able to absorb a blow (especially one directed at the abdomen, but not only there) since the muscles of the body are tightened.
That all being said, I have seen many people breath incorrectly to the point where it seems they are concentrating on sounding like they're breathing out instead of actually expelling the air they just took in. The result is both a loss of power in one's techniques as well as a loss of stamina since there's little in the way of actual breathing going on.
Pax,
Chris
