specifying node.js dependency in both "devDependencies" and "peerDependencies"

I just found out in grunt-contrib-clean package.json file, that it has dependency on grunt that is stated in both sections: devDependencies and peerDependencies, http://ift.tt/1LgnevN:

  "devDependencies": {
    "grunt": "^0.4.5",
    "grunt-cli": "^0.1.13",
    "grunt-contrib-internal": "^0.4.10",
    "grunt-contrib-jshint": "^0.11.0",
    "grunt-contrib-nodeunit": "^0.4.1"
  },
  "peerDependencies": {
    "grunt": ">=0.4.0"
  },

Does that make any sense? Especially, that there are different versions stated? Is it an unnoticed mistake?