rayh, you may not have fully understood the full function of his build as it was explained #1 the max load is 150 lbs #2 the direction of the winding on the strap has a natural tendency to try and tighten the nut and a handle if someone is holding on to it. in order for the load to be raised the handle would first have to tighten against the friction free floating friction plate and the free floating ratchet wheel the spool axle is pinned to the spool, if these were not present than the nut would have to tighten to the last thread.
to lower he merely rotates the handle in reverse if he stops rotating the handle the spool will retighten. If the nut were to be locked on the spool without any additional devices to hold the load then he would simply have to hold onto the handle to keep the load suspended, the one problem here could possibly occur if he happened to be using a socket mounted on a ratchet because a ratchet would be free to turn in the same direction.. but a box end wrench would be just fine.
The only fallacy in his build as designed would be the possibility of slapping a mounted handle to release the amount of holding friction against the ratchet plate and the plate welded to the nut allowing free spin this would result in a free fall. however since there is no mounted handle to the hit in this fashion it is unlikely for this to ever happen you couldn't grip the nut by hand and try to loosen it allowing a free fall.