That is: if we assume zero friction in the bearing at A (which we must), and an absence of viscosity in the medium (air, water, vacuum) surrounding the body (again, we must since we have no information), then the orientation of the mass of the body will tend to remain the same as the assembly rotates around B, simply because there is no force acting on it to cause it to change that orientation.

Yes. That's correct. A better way to think about it is that the body *won't* rotate with respect to the original coordinate system unless you apply a torque, which you apparently aren't doing. So if you put a little mark at the top if it, the mark will stay at the top all the way around the orbit. For convenience in calculating the force on the arm it's nice to have a second coordinate system that rotates with the arm (as described above).

The thing that I implied above might be missing is details of the forces that might be tangential to the surface of the disk/cylinder that would produce rotation, and which it sounds like we can assume are zero.