When I went in for my neurological exam each year, the neurologist makes me grab his fingers in the same way.
Yes, me too, when the doctor saw that my left hand strength was far weaker than my right hand I was immediately admitted to ICU. I was monitored for 24 hours because I was on Pradaxa and it (at that time) had to metabolize for a day before they could attempt surgery. During that day I drifted in and out of awareness and did not even realize that my wife and son were in the room with me. My CAT scan showed a large bleed in the right side of my head between the brain and the skull. The solution in my case was to get off blood thinners. (I am one of those people who bleed where it is difficult to diagnose so blood thinners are a problem.) I won’t say the same is true for Hill, but something similar would account for the neurological episode we saw in the video.