That article comes so close to defeating its own argument it's painful. If that land wasn't protected with zoning, it would have been built up long ago into a typical sprawling suburbia – the opposite of what they propose. So if it had been unprotected in the past, that would have been bad. And if it stays protected that's bad because it's underused.
It is only this short sliver of time that is today that this land should be developed into their dream city. That will somehow miraculously withstand the test of time.
No, it won't, that's just greed and narcissism – thinking that we're so special today that we deserve to have that land unprotected for us but doing that for either future or past generations is a mistake.