3.4 introduces the ability to grant permissions to a User custom field, allowing individual users to be granted permissions on a per-issue basis.

This makes sense for most permissions (Browse, edit etc) but not for permissions that aren't issue-specific, ie. "Create Issue" and "Administer Project". Granting those permissions to a User custom field currently has the effect of granting 'jira-users' that permission, ie. everyone logged in can create/administer the project.