tcoppi is arguing against market cap weighting, which is the reason why VITSX is so close to VFINX despite containing other stocks.
If the total market is outperforming S&P 500, that means the companies not in S&P 500 perform better overall, so giving them greater weight than suggested by their relative market cap would have been beneficial.
Total market has outperformed slightly since 2008, but for a good period prior to that, the S&P500 was outperforming total market (also slightly). It's not super cut and dried.
If the total market is outperforming S&P 500, that means the companies not in S&P 500 perform better overall, so giving them greater weight than suggested by their relative market cap would have been beneficial.