https://unicode-org.atlassian.net/browse/CLDR-14795 is the issue.
Maybe it would help convince them if more Australians endorsed the "Monday is first day of week in Australia" position.
On the other hand, I don't want to overwhelm the poor Unicode CLDR developers with too many "me too" comments.
As an Aussie, I'd love to help you with that haha. Unicode is wrong ;)