What you are failing to understand is that if you are training for an instrument rating, then presumably you are operating the aeroplane under IFR, whether that entails simulated or actual IMC is meaningless. In operating under IFR, you are required to be appropriately qualified in order to log time as PIC i.e. you need an instrument rating!
The regulations (FARs, CARs) permit a student to log PIC time WHENEVER he is the sole manipulator of the controls of the aircraft for which the student is rated. Whether the flight is conducted under VFR or IFR here is irrelevant because a student during his training flights will ALWAYS have an Instructor with him on the right seat.
The ONLY time a non Instrument Rated Private Pilot can log PIC and the Instrument approaches and time, is when the flight is conducted under VFR and he/she has a SAFETY PILOT on the right seat who is appropriately qualified. In such flights, the Instrument student requests for a "Practice Instrument Approach" from the ATC.