Interesting thought. I think it's important to add that the pressure of the right index finger (for a righty) isn't felt until near impact. At impact, this would ideally result on the hands leading the shaft and clubhead through the ball. In effect, the shaft would be "leaning" towards your target, which would feel like pressure against your right index finger.

Two notes: Jack said he could take his right index finger off his hand without affecting his play.

Any tension, especially introduced mid swing, in the fingers, hands, arms, or shoulders will kill your swing. Feeling pressure against the finger by properly handling the club shouldn't be confused with the idea that you can properly handle the club just by squeezing your finger.