Hello,
I've re red the article and it does not specifically say why the heavier oil mix makes more power but I'd wager it is the result of better ring seal. That's all I can figure.
As far as exhaust smoke and cleanliness all of that is more a function of tuning than mix ratios. I used to work for a public municipality as seasonal help and part of my job duties was to keep the sidewalks clean. There were over 2 miles of side walk at least 8 feet wide that we cleaned twice a week in the summer. We used echo back pack blowers to do this. I mixed my own fuel with what ever cheap oil they bought. What ever it was was elcheapo petroleum that simply said to mix to manufactures instructions. I didn't trust the oil and in an effort to be socially unacceptable I mixed the oil heavy. I wanted a lot of smoke. The more the merrier. I don't care too much for tourist. I would keep the carbs tuned so the blower made good power. The result, no smoke, no dirty exhaust, nothing. I got to the point I was mixing at more than 8:1 in my quest for a smokey mess. The blowers never did protest. In the 6 years I worked there I was the only one that touched the blowers. They never even needed a spark plug, and I never did cause my smoke screen.
bullittman