I'm convinced that strong no-hands low-speed shimmy is related to some kind of wheel tracking problem. I have cured that kind of shimmy by aligning the rear end of a bike. OTOH, I have seen forks that weren't aligned on bikes that didn't shimmy at all. People report that fork alignment problems can cause shimmy. No-hands shimmy seems to be more prevalent the less trail a bike has. So front weighting those is a good idea.
The pros are on bikes with a lot of trail. Probably has a lot to do with their lack of problems with shimmy. I am a little surprised they don't have high speed shimmy/speed wobble though.