That's fair, and it's one of the reasons behind the 20% holding; it should also reduce expected volatility. The recent underperformance highlights the risks behind our sector concentration, which is my main issue with the index. Expected long term returns are still almost equal for domestic/international, so it could just be short term volatility.
Some home bias seems reasonable but it can be difficult to find good information as discussion is usually focused on dividends and currency, which should be immaterial.