There's a "Notice" on these changes from the DAFF
on their website where they state the reason for the change was :
The amendments reflect scientific advice on goods that pose an unacceptable level of risk.
The amendments will allow DAFF to better target and intercept goods that are a significant risk to Australia’s agriculture and environment, such as raw meat, seeds and fresh fruit and vegetables. The amendments will assist in enabling the more efficient clearance of increasing international passenger volumes while allowing DAFF to focus on targeting what matters most.
I still think the "dairy" part is at best confusing, and at worst outright wrong. It's being used as a noun, and according to my dictionary the noun definition of "dairy" is "A building, room, or establishment for the storage, processing, and distribution of milk and milk products." Now if anyone is actually bringing a "dairy" into the country, I think they have bigger problems than question 6 on the form...
If they actually mean any "dairy products" (products "Containing or made from milk") then they might as well left the original wording of "food" in there, as there aren't going to be too many food products that don't contain at least one of the items listed...