The definition of 'instrument flight' is not a constant.
If one is under training for a PPL, the flight would typically be conducted under VFR, the instructor logging the hours as VFR, perhaps with a remark that the lesson was instrument flight. The student, however, logs the time as instrument flight and in the P.u/t column.
The logbook definition of instrument flight refers to the legal rules of flight, IFR or VFR.
I once filed an inflight IFR plan, and as soon as this was accepted called field in sight and was cleared a visual approach, managing to log 15 or 20 legal IFR minutes ; I was desperate to maintain my IFR time.
Point is, it was instrument flight conducted entirely without reference to the instruments!