Hi,
Good question! Bill is pretty outspoken but plenty of people disagree with him!
The one thing scatter winding does do is break up the wind pattern and lower capacitance as the wires are no longer running parallel to each other. Capacitance effects the tone by rolling off high end, same problem you get with long guitar cables. So there IS a tonal difference, more harmonics.
Downside is that no two humbuckers can ever be identical, having said that BKP scatterwound pickups are pretty close, that's just because of close tolerance and accuracy!
As the other guys have said, scatter winding is only part of the process, an important part granted but there's more to a pickup than the way it's wound.
Don't forget that a big part of the early PAF sound was down to the hand winding which naturally produces scatter. Leo Fender also new the benefits as he resisted the move to automated winding machines!
the biggest problem is that scatter winding takes a fair degree of skill, serious hand strength and lots patience. It's not a way to mass produce pickups or get the biggest profit margin
