Inserting the muzzle ahead of the bird sounds a whole lot like spot shooting to me. But then I try to point in the general direction of the bird, rather than the general direction of my pointing dog's head. The bird's usually somewhat higher than the dog, and I'm sure the dog appreciates my caution.
The problem with sustained lead while hunting is that, unlike on the skeet field, you don't know how far away the target is. Hence, you don't know how far you're leading. That can be especially problematic when you have a bird that's significantly different in size (like a pheasant) from the clay birds you're used to shooting. It should work somewhat better with quail, which are similar in size to a clay bird, although there's still the distance factor to deal with. But a 40 yard rooster is going to look about the same size as a 20 yard quail, and is likely to give one trouble figuring out what 3 or 4 feet of lead, or whatever it is, actually looks like.
The advantage of a quick swing-through, which doesn't take nearly as long as some might think, is that you know one thing for sure: your gun is moving faster than the bird. Otherwise, you could not catch it and swing through it. The result is built-in lead, plus the fact you're swinging the gun to establish it. You insert in front of the bird and you can end up stopping because you haven't yet started your swing, and the lead looks right.
The one problem with swing through and a light gun is that light guns start fast and stop fast. Easier to keep a heavy gun moving. That being said, if you shoot enough with light guns, you overcome the tendency to stop.
