Well, it seems to me, while driving my FR-S down the highway, if the steering wheel rotates far enough to whack my thumb .......I would be heading off the road at about a 90 degree angle ....... and a sore thumb would be the least of my worries.
So, since I'm not off roading or driving a dump truck, I allow my thumbs to help hold onto the steering wheel......
Now, back in the day ...... crank starting a machine ..... was when you DIDN'T want your thumb wrapped around the crank.
Who can tell me why ..... and how did you find out .......??
humfrz