I doubt if it is a mistake. The same thing happened to me...a couple of the schools that I applied to last cycle decided to make Anatomy and Physiology required instead of recommended coursework... I got conditional acceptance pending I finished that course before school started. I am taking it right now, It ends the beginning of August and school starts for me August 19th. If you can't fit it into your schedule (AND you really need to if at all possible) you can ask can you take it over the summer. I don't think this is the norm, but hey, an acception was made for me....keep in mind they had already interviewed me by the time I asked could I take it over the summer, so I think they already knew they wanted me. Not sure if they would be so willing even before you were invited to the interview.
PS, the second school would NOT let me take it over the summer, so it just depends...
Good luck