NSW reopening on Oct 11, page-54

Could someone please answer as I am not understanding.
Both vaccinated and unvaccinated can catch and spread the virus.
I understand that if you have been vaccinated symptoms will be lower than the unvaccinated.
SO the question is why is there a vaccine passport?
Only explanation is that the viral load in the unvaccinated is higher and they can spread it more readily.
However can not find any evidence of this with statistics.