He likes it because it can strengthen planning of where and how development can take place. He likes it because it can push his vision of "sustainable urban form" retaining urban growth limits. Given he says it is good for the environment, you can see where this is heading. Greater Auckland City will be a behemoth of a planning monster.
The debate, of course, should be what is the role of local government?
Until you answer that question, the form it would take is pointless to discuss.