Yeah, the smith machine seems an odd choice, but nothing stops you from adjusting this part and do it free weight.

I enjoy the Smith Machine. Makes the exercises go faster by using one machine which I think is the intent of circuit so you can increase heart rate and keep it up. The only issue is that the Smith Machine doesn't allow for the full range of motion but I fixed that by adding an aerobic step between the columns that way I get full range of motion and don't hit the stops/spring at the bottom of the deadlift.