Each of you make good points from a personal perspective. Here's mine:
I've flat tracked, hill climbed, and rock crawled scree slopes and boulder fields on enduro bikes and encountered all the events mentioned above, and never experienced an inadvertent throttle roll.. You grip it with your whole hand, you know? If your fingers are crooked it just ain't gonna roll itself. I'd think fine throttle control would be enhanced considerably. To me the thumb throttle just seems too be an unecessary and very physically limiting design factor.
After 45 years living with twist throttles under all kinds of crazy conditions, they just seems natural an natural extension of my arm.
I'll try it..and can always go back.
Thanks for your perspectives.