score:8
There are definitely no citizenship, age, or ID requirements for entering the Japanese cemetery and gardens. It's been several years since I was there, but realistically there is no way such restrictions would ever be enforced - plus they would almost certainly be illegal under Australian law (discrimination on grounds of race/citizenship).
I suspect this is a case of something being lost in the translation - perhaps to "enter" the cemetery (ie, be buried there) you had to "present a Japanese passport" (ie, be Japanese)?