buffeting when landed

Playing the Border campaign mission 2, I noticed when landed and picking up the special forces from the base, collective fully dumped and parking brakes on, that as soon as the troops had boarded I started to get the buffeting and vibration sound that you normally get as you transition out of translational lift. I just thought it was odd to get that sound while not moving, not sure if that's a bug or a feature of being heavily loaded, but I had never noticed it before when loaded and stationary.