Citizenship Test

So I saw that a new Citizenship Test was introduced and I figured I would read through the guide they provide to help people study for the test. I was so alarmed at what I read that I wrote a letter to the Department of Immigration and Citizenship:

I am an Indigenous Australian and I thought I would read the booklet "Becoming an Australian citizen" to see what information it was providing about Indigenous people.

I find the following passage disconcerting:

"On some mission stations and reserves, settled communities began to emerge. This worried the governments for a growing proportion of the people on the reserves were mixed blood. Though full-blood Aboriginal people were disappearing fast, it looked as if there would be an ongoing separate group of Aboriginal people."

I do not understand what this passage is trying to say and neither did my colleagues. It seems to imply that "mixed blood" people are separate from other Aboriginal people and that this group is a group that causes worry. I am concerned that if myself and other Indigenous colleagues don't understand this passage, what chance do potential new citizens have and what message does it leave them about Indigenous people with a mixed cultural background?

As yet I haven't had a reply, but I will post whatever they reply when it comes.