Actually, IIRC, big fans like the JT9D's the graphic cone of danger is actually 20 some feet in front of the engine at full rated power. There is an extreme danger depiction at something like ten feet. The cubic volume of air being affected is enormous at max power. Enough to suck passengers into the engines off the upper deck of United in Hawaii.
Blame the operator? That's silly. The rated and qualified mechanic or pilot in this case was probably blameless. He can't see what's going on from upstairs. Tethers? Ridiculous. We have a bad enough tripping hazard with just the fuel static line.
Working around spinning props is even more dangerous, but mechanics must do it. One second of absent-mindedness and you've just walked into oblivion.
When I was 22 we couldn't get the second engine started on a Falcon 20. The FBO's gpu had already taken off (they didn't wait for anything.) No Apu. I told the captain I would drop the aft hatch and climb into the tail to bang on the circut breaker panel that we knew housed the sticking relay (while he pressed the start button.) The captain reluctantly agreed. On the way to the hatch in the dark, I passed by the running aft-fan (fuel sprayed) GE CF700 tail pipe. Even though I was partially leaning forward, it burned the hair off the very top of my head. Man did the smell of burning hair smell bad! If I'd have been any taller I'd have been in bad shape! Got it started though.
Later that year, an Evergreen mechanic from Marana was in Phoenix meeting an Emery DC-8 that had lost nose gear steering out of SFO. When the jet stopped the 21 year old mechanic climbed into the nose wheel well to survey the problem. Bang. Crash. The nose gear retracted cutting him into pieces. Don't know if it hurt anybody on board, as it was quite a fall, but it was certainly a horrific sight as we parked right next to them after it happened.
Young men make stupid mistakes sometimes in aviation. It's still the safest form of transportation ever devised. And definitely safer than roofing!