(as an outsider looking in) I think, for YC, who pride themselves on their tight-knit alumni network and reach of their partners, in-group bias was always going to be a self-fulfilling prophecy.
There are no rules about these kinds of things in private organizations, so it defaults to the instinctive human behavior.
Whenever you hear about the "greats" of the industry, you can be aware that they rose to prominence through navigating power structures built on such principles.
