(referring to : kick is blocked, batted backwards by B behind the NZ, ends up in B's EZ without B touching it beyond the NZ)
If the ball touches the ground in the EZ, or is recovered by B and not brought out, or goes OOB in the EZ, we're probably all agreed it is a safety.
The only problem is if A touches the ball in the EZ before it becomes dead, and there seems to be a contradiction between the impetus/safety rule and the IT rule, where B would end up with ball at their own 20.
I'd still go with the safety, for the time being.