I was working on a job once when one of the roofers came up to me and told me that the temporary steel safety cable outside on the roof was live. I knew that wasn't possible because the steel cable was threaded through angle iron that was welded to building steel. But I went out to check anyway and to show him the cable was not live. I took my Fluke meter with me.
As I walked across the rubber roof membrane (the roof was not finished), I realized there was a potential for static buildup. The soles on my shoes did not allow for static buildup as well as the soles of the roofer's shoes. I touched the safety cable and got a mild shock. He touched it and you could both see and hear it. And he jumped. The static buildup in him jumped immediately to a ground source. And it would do the same while using a dust collector, if it had the chance before dissipating.
Electrons take the path of least resistance, and yes, there may be many paths. Seeing a lightning strike shows that clearly. The charge is looking to find it's way to ground and will take any path to get there, as quickly and easily as it can. But it's kind of like a highway, if the roads are packed, you take another route, e.g the path of least resistance.
I've done a few lightning protection jobs. Most people think the purpose of lightning protection on a structure is to attract a lightning strike. But in fact the actual purpose is to dissipate the charge and reduce the positive and negative charge differential in the air. To do that you place sharp pointy spears all around the perimeter of the top of the structure and bond them to a known ground with a conductor sufficient to handle the potential load. If that "highway" gets overloaded, you could have a problem.
The unknown variable with static buildup is how much of a charge is building? While you're sanding away, you can't feel the buildup. And there's nothing to measure the buildup. Typically, a person only knows there's a buildup when the it suddenly discharges, or when their hair stands on end.
I was a foreman on another job when I arrived at work one morning to see my boss throw a smoking telephone out the trailer door. He screamed as he did that, obviously shocked. I walked into the trailer and he said he was talking on the phone (land line) when it started smoking. Next thing I know the iron worker foreman in the trailer next door comes over and says his doorknob is live.
I took my Fluke over and sure enough, the doorknob to trailer's steel stairs read over 50v. The stairs were free standing and now on damp ground from rain the night before. I looked to see if the trailer was grounded. It was. I was scratching my head. Then one of our guys came out of the building and said some of the temp lights were out, some were dim and some were bright.
I went on the hunt to find out what was going on. In the process I also learned the skip (manlift) wasn't working and found the controls were fried. In the end, we finally agreed the building must have taken a lightning strike the night before. Lightning protection was not yet installed. The charge took whatever path it found and damaged a few things along its way to ground, one of them was one leg of the 3 phase temporary transformer.
I've seen some pretty crazy things in my career and I've learned that electrons are unpredictable in an uncontrolled environment. While they ultimately make their way towards their final destination, the exact path cannot be predicted. So you do your best to direct them along the way and help them discharge as quickly as possible so they don't do any damage, and try not to allow yourself, the tool you're using, the dust hose or the vac components to become capacitors. And that's what tells me it's best to make sure your expensive dust vac is protected from that stray charge trying to jump through sensitive circuitry.
Maybe the Festool anti fatigue mats should be anti static as well with a binding strap.