Cannot set deployments as zipped on EAP 6

When you add a new EAP 6.1+ server, open the server editor and go to the Deployment tab, the "Deploy project as compressed archives" checkbox is greyed out, so you cannot check it.
This doesn't seem to be part of disabling any editing when the server is in an unsafe state - I can change other deployment settings.
Maybe it's because I have no project in the workspace, but I can't see why I still shouldn't be allowed to modify this.