Most of the post are from YC companies that haven't publicly announced that they're part of YC, hence the secrecy. Often they'll want to announce the YC connect

Most of the post are from YC companies that haven't publicly announced that they're part of YC, hence the secrecy. Often they'll want to announce the YC connection as part of a press release as it helps them get press coverage, and they don't want to lose that advantage.