Even if this was the case I doubt it would create a strong enough vacuum to move the lid. I think the threads just slope downwards a little more than other jars

Even if this was the case I doubt it would create a strong enough vacuum to move the lid. I think the threads just slope downwards a little more than other jars and they let gravity do the rest. Maybe the lid is lined with a slippery rubberized material that creates a seal, which would minimize friction allowing the lid to spin with minimal force. Edit: if someone has one of these jars, tilt it a little and then try lid trick. I bet it won't work.