Ann: Class Action Settlement, page-30

Yes, unless you go to the trouble of inserting a dictionary into your contract, someone will always claim one word or paragraph means the opposite of the intention. The Acts Interpretation Act 1901 (Commonwealth) seeks to at least avoid arguments over "may" and "must" by telling you how those terms must be interpreted in all Commonwealth legislation. There are state-based equivalents too.
In regards to the specific situation with TGA, I think they just wanted it to go away. Legal action is inherently unpredictable even for "strong" cases.