well the polyps will sway if they get hit by flow. if they're not moving at all, definitely nothing's hitting them. What really matters is the massive water moving past it, rather than it getting blasted by flow. It just needs water to move against the polyps in whatever form. Turbulent is better because it'll probably cover more even of a space, but direct is bad because it'll blow the tissue off.
You should see my millipora, it's long polyps don't sway, they fly around like crazy. Kind of like if you had a flag outside your car going at like 70mph. The polyps flap and flicker everywhere like crazy. It's been that way for months, and it's lovin it =)