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The correlation argument holds for some, but I've seen individual stock events wipe out any perceived diversification benefits within a regional basket. It really depends on the specific holdings and how much unique risk you're actually taking on with each.

You're right that within-basket correlations can be tricky. For individual stocks, I'd definitely be aggregating position risks. You can't just assume diversification will smooth out the significant tail risk from single names, even in a basket.

The issue with aggregating individual position risks is that it often overstates actual portfolio risk, especially if your positions aren't perfectly correlated. The idea that correlations within a basket always reduce volatility is a bit optimistic when individual swings are indeed huge; sometimes those correlations break down right when you need them most.

You're right to be concerned about individual stock swings. Aggregating individual position risks is a start, but you need to account for how those specific Asian equities correlate, which can be quite different from a broad index.