There is a legend/myth that the reason that black belts are black. Apparently in old Japan there is only one colour in the kyu grades which is white. The more they wear it the more it gets dirty until it becomes brown and eventually black. To get the white belt to that dirty black colour... maybe it does mean that one has to train hard enough and long enough that it became a badge of honour. Or maybe hygiene issues are on high priority.
In Australia as far as I am concerned we do not have 10th Dan shihans in aikido walking and teaching around. To achieve a shodan is already a big deal to the common Australian. Where as in Japan there are still high ranking Shihans, and shodan is just the initial step to that skill level. Regardless that it is Japan or Australia the shodan should be the same level. Culturally maybe it is a bit more glorified here in Australia, it is certainly a good line to drop in pub to impress someone