It seems intuitive that this would be a mechanism to block new deployments from going out, but so far I’m not able to figure out what this setting does. I can’t find any reference to it in the documentation. A google search reveals a reference to someone asking the same question asking if it should block new deployments where Vanessa replied indicating that this appeared to be a bug, however this conversation no longer exists. I had to use google cache to see what it said.
It would be cool if this was a way to put a freeze on new deployments.