From what I can tell it happens on these and even OEM Xenons. The problem is a lot of people are told by others to "seal the lights up tight" using grommets etc but in reality that's the wrong thing to do. Air flow will keep them clear. My old car had OEM Xenons and they misted as one of the air vents was blocked, after I cleared it there was no more condensation.
If you seal them up air tight they will act like any old window with an internal/external temp differential and in turn cause condensation.
Edit: I understand people use Silica Gel packs to keep them clear too which is a good idea.