Part of it would have been access to YC deal flow, sure. But to me it was also like an index fund - i.e. invest in the basket of companies rather than picking

Part of it would have been access to YC deal flow, sure. But to me it was also like an index fund - i.e. invest in the basket of companies rather than picking and choosing because on aggregate the group is going to do very well. Really, you're blind betting on YC having chosen a few winners in the cohort. Not a bad bet to make!