Manufactuer just as culpable:
Seems like they should’ve made the elevator/stab gap larger than the length of the screw. Such a tragic way to discover the flaw.
Ope, you are correct. At least partially this is one of the risks of operating an experimental aircraft-in theory all the red tape and overhead involved with certificated aircraft is supposed to minimize this kind of thing, though obviously with varying degrees of success over the years.
Or the screw shorter than the gap, or put the access from the outboard end…easy to see in retrospect, but probably not so obvious in the process. It’s also unfortunately not that uncommon for GA aircraft to have fasteners in the tail cone area that can do this kind of thing (thinking specifically of PA32/28 tailcone screws, IMS the caravan had something on the elevator horns that might have been similar too), but usually the hardware is flimsy enough and the aircraft stable enough that any binding can be overcome without losing control of the aircraft. That chonky plug, plus an airplane with minimal stability to start with appear at first glance to have been holes in the Swiss cheese in this case unfortunately.
