No, I think what he is saying is that beading does not cause spotting.
You should remember I am new to WFP so my post might be wrong, but the way I see it, If the water is truely pure and the windows are clean where are the spots going to come from?
Beading glass is more prone to spots, but it isn't what causes it. Bad rinsing, dirty frames, back splashes and unpure water are the causes I think.