Ann: Change in substantial holding, page-2

So that is one institution who is still buying after the merger annoucement.
But what are the disclosure laws here?
Some of those purchases listed in that annoucement were from back in June last year. They were already a 'substantial' holder (over 5%).
How long are they allowed to wait by law until they have to submit the 604 form (change in interests notice) to the ASX for any change in their holding?
6 months later seems a bit rich.....