My recollection of the Gazelle accident was that he lifted into the hover to do a compass swing. The problem with an unlatched P2 belt falling into the cyclic mechanism is a known problem in the Gazelle. Which is why, IIRC, it's a checklist item to insure that it's done up.
Edited to add: Just found the AAIB report. http://www.aaib.dft.gov.uk/cms_resou...pdf_028729.pdf
I follow the same logic in whichever heli I fly. The P2 belt remains done up, regardless of whether the seat is occupied or not.