Basically there are two systems of recording time under IFR and/or time flown by sole reference to instruments.
Whichever one that is used depends on how one operates and how easily one can record the actual amount on sole reference time actually done on an IFR flight.
For anyone inspecting a logbook, the system used becomes obvious from the records. If a flight of 1 hour has 1 hour instrument time then that pilot is simply recording all IFR flights as instrument flights. If the instrument time is less than the total flight time then one can take it that thye are only recording actual instrument time.
The CAA will give the IR pilot who records flight by sole reference to instruments some credit for the hours required to instruct.......and they use a factor of 4...........which seems resonable for UK/ round Europe operators i.e. you will on average spend 1/4 of the flight time in IMC on IFR flights.
Using the CAA's system one can easily inspect a logbook and decode which system the pilot is using and then factor if required. Anyone with experience can easily detect significant amounts of Parker Pen flight hours.
If one was being pedantic then the experienced PPL with night qualification would have lots of instrument hours no matter which system one uses because ther are periods of visual night flight when the instruments are the sole reference.
Overall what we want in an IR pilot is ability to operate in the airspace and naviagte to the required accuracy and make approaches safely to the specified minima regardless of the flight conditions............lots of IFR IMC bimbling in Class G acheives none of that regardless of how it is logged.
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Tim,
Very important point - IFR flights are not separated from VFR flights in Class D.
Regards,
DFC