I have worked under and around heavy equipment for many moons. I have had to chain heavy rocks and heavy logs in dangerous situations.
That slab was being moved in a very delicate situation with that standing payloader so close to the end of the slab away from the worker.
A slight slight nick of the slab against the machinery and some very unexpected results could occur. The worker, if you will observe, was howing, what to me, a great deal of inattention to the moving load. Granted, there was not much space for him to move further away and i am sure he had complete faith in the fork lift operator's abilities. If i were workin in the same position, i would have been paying a whole lot more attention to the movement of slab and machinery.
When he was placing the piece of wood under the slab for the forks t bet under, the load was only being lifted enough for clearance of the wood and then the forks were moved in further. The space for the worker to move into was very uneven, but still there was room for him to move. Whether he could move further or not, you will notice he was NOT really paying very close attention to the load as it was being moved into a space that was very close to being directly over his head. Even if it was not directly over his head, a nick against the other machine could sent the load sliding.
When I was doing masonry, i often called on a very good friend to bring his machine to my job (where ever it might have been) to help me retrieve or place huge rocks. I would do the chaining and unchaining and he would operate the machinery. While i was chaining, he would take his hands completely off of the controls to avoid any unconscious mishaps. Once chained, the load would not be moved until i was well out of the way for any accident that might just happen. If the stone was to be placed on a wall, there was an extra guide chain or rope attached so I could be well out of reach should the rock (or log) come lose. Over the course of 20+ years, the two of us moved many loads with no injury. Even tho we were a team, i never took my eyes off of the load or the track of the load and its relation to me and where i was going to put my feet was of utmost importance. That young man was somewhat oblivious to both. The machine operator had a tight squeeze but I would say he was quite capable and perhaps the camera angle made the operation look tighter than in reality it might have been.
Tinker