Ask HN: What does "Recent Grad" or "New Grad" mean?

I see ads for Data Scientist positions in the SF Bay Area that are labelled "Recent Grad" or "New Grad," from companies such as Khan Academy, Twitter, Netflix, Linkedin.

I was surprised, and somewhat discouraged, since I thought this was not legal, but these places are big enough to afford lawyers, so perhaps it's OK. But even if they can't come right out and say "age-limited job," there is a clear hint as to their intentions.

Has anyone outside of the requested demographic had experience answering these kinds of ads? Were you able to get an interview? What does "recent grad" really mean in this context?