For me the pinching would occur somehere in the middle of the tube between rim and tyre, on a tubeless designed wheel without rim tape or spoke holes. Didn't use any powder which might have been a mistake. The flats weren't dangerous on the road, but if it happened on a fast descent, yes, that could be.
I did notice a (positive) difference in ride feel between Vredestein latex and butyl, but the issues with the tubes led me to go tubeless.