The dust extractors are shop vacs, really nice ones with good air sealing and filtration, they don't leak fine dust from every crevice and they do a much better job of keeping things clean, I have no hesitation of picking up water with any of mine. So long as you use the foam filter to keep from pulling water into the motor your fine. It is a plastic tub people, no matter how much you want to make it more in your mind, it is a plastic tub not rocket science.
As for Scott at festool I can't say how much time he has running them, but personally I run festool vacs 5 days a week and have for about a decade and feel confident saying I have no fear in using them to pick up water and anything else I encounter on a jobsite. If a vac can survive drywall dust then water is not a problem.