If there is a problem that shuts off the breaker the PDU is attached to you will lose a large section of miners. Having a breaker trip and 4 miners shut off is much more desirable than losing 12 at once IMO and if you have a melted plug or something else that needs to be addressed there will be a ton of downtime.
You are right. What I was trying to say was that the geist PDU supports one 20A breaker per every 2 miners. That way, when something melts or arcs only those two miners go offline instead of the entire PDU. I don't use these PDUs myself but they work well from what I have seen.