Actually you are somewhat correct. The knife is held BOTH ways. “TRAINED” users would use it as you described.
What are the chances this guy was “TRAINED” in the use of this knife? or would he hold it like a plumber?
AND.... maybe it was just “KEYS”. Is there a proper way to hold keys? For defense I mean. /s
Naw, I’m not somewhat correct, I am trained in blade arts.