One of the main factors in operating equipment safely is being able to stay focused on where your hands are in relation to a spinning blade or bit. Staying focused on where your hands are in relation to 2 spinning blades or bits is quite a bit harder. Unless the person is confident that he/she can stay that focused-or- be able to overcome those problems with push blocks, featherboards, etc, then I would say stick to one operation at a time.
Someone I consider a master woodworker once told me that a master woodworker is not someone who never makes mistakes. He is someone who is able to cover them up so that no one can tell.