WONG'S LESBO MARRIAGE, page-113

True story: The marriage act didn't refer to "a man and woman" getting married until John Howard quietly changed the Act while he was prime minister to block gay marriage.

I’m not a legal person but there is always two aspects to legislation/law to look at.

Besides the actual written wording u need to also consider the intent of wording.

Previously, the intent was defining that marriage was between man and women.

JH simply clarified what was the intention of the original legislation.