In practice, GPS receivers are typically accurate to no more than 3-4 meters under good conditions (open sky, no obstacles), so even in Australia the difference

In practice, GPS receivers are typically accurate to no more than 3-4 meters under good conditions (open sky, no obstacles), so even in Australia the difference between WGS-84 and a datum locked to the plate isn't enough to matter for navigation. Specialized equipment can use GPS to produce more accurate measurements, to the point where these things matter, particularly in Australia which as far as I know is moving fastest relative to WGS-84.