Unlike the more widely referenced HSI Hang Seng Index of Hong Kong which is dominated by Chinese stocks listing on Hong Kong market, MSCI Hong Kong Index only have ~6% stocks controlled by Mainland Chinese entities and another ~6% stocks that are significantly and directly exposed to behavior of Chinese consumers (For example companies which main business are casino in Macau and such). Hence it is more capable of reflecting the economy of Hong Kong.
However, EWH being an ETF that track the MSCI Hong Kong Index, does not appears to benefit from this distinction.