Yes. Odometer reversal is difficult to detect, however, at the same time, I think, its reversal also seems very difficult (almost near to impossible) in Japan too! It may be a serious crime there.
Japan is a developed, well-educated and honest country, unlike us (unfortunately). And I hardly think, they can even think about doing it, ever! Their whole system will collapse and trust lost forever, since their vehicles are not exported to Pakistan only, but in other developed countries too.
These bad things, I believe, are done by dishonest importers here, and may be, when car reaches Karachi port or may be during transit, but I am not sure. Only those people who have first hand knowledge / experience, can shed the light better!