Her pointing out that a man made a decision that is common and one that he benefitted from, is not her saying he can’t be female because of that decision.
Put the statement back in context, she also referenced, before making that statement you consider significant, about how he was awarded a ‘woman of the year’.
It was her way to pointing out that he could achieve that award because of the success of his career which was supported by the mother of his children making the decision she did. Leaving him free to pursue success which led to supporting him gaining an award. (One meant for women)
You drew a flawed conclusion from her statement. You also removed important context about what she was referring to.
“a man who has lived for 40 years as a man and had children with a woman and enjoyed the services – the unpaid services of a wife, which most women will never know ... then decides that the whole time he’s been a woman.”
This above was a follow on statement to the comment about the women’s award Jenner was given. Context matters.
But getting back to what you seem to be attempting to claim.
Typical family decisions such as who is the primary carer, who of a couple may make a choice to not follow a previous career path but to look after the children, is just as weak as a tool for categorising sex classes in humans as personality traits.
She used the decision that family made to highlight the fact that Jenner benefitted from being male, while then declaring he was female. And then winning an award that was meant to recognise female people’s achievements, while he achieved the success he was awarded for as a male person.
She did not use the statement in any other way, in my opinion. She didn’t say ‘Jenner cannot be female because of the decision the family made’. That would be absurd. She used the statement to highlight the fact that he is male and he used the advantages of being male that he started acquiring from birth to his benefit.
Not that anyone making that same decision must be ‘male’. Because that too would be an absurd statement for Germaine Greer to make, given her many words in the past that would contradict such a statement.
If your assertion is that she declared that because Jenner didn’t choose to be the primary carer that Jenner is therefore not female, I think you have misinterpreted what she intended as I and others have pointed out.