Yolngu reckoning of the year does not separate the sky from the rest of the evidence. A season is identified by what the stars are doing, what the wind is doing, what is flowering, what is fruiting, what is spawning and what is safe to eat, and the sky is one indicator among several rather than the master clock.
That is a different design from a calendar. A calendar predicts; this reads. If the stars say one thing and the country says another, the country is not overruled, and the season is what the whole set of signs together indicates. In a monsoonal climate where the arrival of the wet varies by weeks, that is the more robust method.
Djulpan sits in this system as a marker rather than as a date. Its rising in a particular orientation belongs with other signs of the same period, and its story about the forbidden fish belongs with the rules about what may be taken when.
The Yolngu material is unusually well documented for Australian sky knowledge, partly through long collaboration between Yolngu knowledge holders and researchers, and partly because bark paintings and ceremony have carried it in forms that could be shared. Much other Australian sky knowledge is restricted, is held by particular people, and is not published. The absence of an account in the literature is not evidence that there is none.