The MRT member would have been on the end of the hoist-cable in a 'NATO Strop', which goes over the head & sits under the armpits. A toggle is then pulled down to provide a snug fit & prevent the wearer falling out. Unless one put ones arms straight up over ones head it is virtually impossible to 'fall out' of the device. I suspect it was a conscious decision to get out of the strop, although the individual concerned cannot remember much other than feeling a very rapid RoD.