I'm not sure this is up to YC. I doubt they want to go to everyone they're trying to fund and ask permission for this nor do they want to deal with potential investees feeling like their trust has been breached.
Furthermore it's probably in YC and their founder's interest that people not know what they are working on until they feel ready to disclose it.
Furthermore it's probably in YC and their founder's interest that people not know what they are working on until they feel ready to disclose it.