That’s not my understanding of how the ATO would treat that...

That’s not my understanding of how the ATO would treat that transaction for tax purposes it would be 20c-2c given the immediate off-market transfer at 20c (exercised on 22/11 sold on 27/11 would qualify), not 27c.
18c x 90.198m options = 16.26m
@30% that equates to $4.8m tax liability
@47% that equates to $7.63m tax liability
The transfer of 45.1m shares netted $9.2m.
whichever way you cut it the tax event is below 50%
The announcement does not mention the funds being used for the exercise of the options only the tax event.
I am wrong more often than right, and I am certainly not a tax expert even though I should given how much bloody tax I pay, but to me an exact 50% sell down is not explained by the content of the announcement.
If there were other reasons then it would have been advisable to disclose them, including taking some chips of the table, alongside the names of the investors.