I think your logic is sound, but I assume the folks who claim 'you can't trust the numbers coming our of China' are probably assuming that the numbers are being

I think your logic is sound, but I assume the folks who claim 'you can't trust the numbers coming our of China' are probably assuming that the numbers are being intentionally underreported for political reasons. I have no idea how those numbers are generated, but I suppose it is at least in the realm of possibility that they could be deliberately reporting lower numbers, and it is not like anyone can really check the math with out doing some extensive verification. Regarding the fact that the death rate appears to be lower outside of China, that would appear to provide evidence against China mis-reporting their numbers (after all, why would they intentionally report a higher death rate). But the one plausible counter point that I have seen, is that the hospitalization/ICU rate is pretty high, to the point where a wave of COVID-19 infections in a short time-span could overwhelm local capacity causing a large spike in mortality. This is most likely why China was building Hospital facilities in Wuhan and why they imposed such a draconian quarantine. So the numbers outside of China might not really be comparable because the number of cases (so far) have been well below local hospital capacity. Unfortunately, it looks like we are going to have a third data point soon. Iran has really poor healthcare infrastructure and they are undergoing a wave of infections. If the mortality rate is heavily dependent on ICU treatment, then Iran might be close to the worst case.