It sounds like YC serves as a vehicle to bring deals to YC partners, who make a killing funding the most promising candidates from the YC batch. This has made so much money for YC partners that they still want to continue to pick winners, but they don't want to kill the golden goose, so they withhold their blessings for three weeks. YC companies will still prefer the partners for funding over some random VC, so they still get the deals, but now the relative losers from the YC batch will get more funding from the more clueless VCs.