To be honest, I don't think that you need to know the history before an interview. Before I applied to and interviewed at MD/DO schools, I knew absolutely zero about the history of osteopathy. Couldn't even have told you that A.T. Still founded it. I was, however, familiar w/ the theory and practice b/c of knowing DO's. I was very surprised this didn't come back to nip me in the butt at Kirksville, but oh well...
Now, as an interviewer, I can honestly say that I have never heard anyone in any of my groups ask a candidate anything that would require a knowledge of the history of osteopathy.
Once you start classes here, we have a short course w/ two exams that covers this topic.