Could be…but i would think that rule would come from corporate Nikon and not the country one so it would be the same for everybody.Nikon Australia may not have imposed the same limitations as Nikon USA. Just a guess.
And following on another comment…the fact that it isn’t as good wide open as stopped down a stop isn’t surprising at all…given the price, zoom range, etc. Personally…with 5he outstanding noise reductions d sharpening software we have now…bumping the ISO a stop or the shutter a stop slower and shoot a burst will solve this issue most to almost ll of the time. And…part of the issue as others noted might be technique…or the fact that he’s not normally a Nikon shooter so might not really know the AF system well enough to pick the right one over the almost right one.