FWIW I spent a fair amount of time yesterday flying through clouds in my Vive Pro using our latest internal beta release, and did not see this effect although I was looking closely for it. Cautiously optimistic we've finally found a way to eliminate this.
So I can be sure, can you let me know what graphics settings you are using (AA setting, HDR on or off, Vulkan on or off?) These sorts of issues are related to the depth buffer, and X-Plane handles the depth buffer differently in each of those cases.