As stated before, it must be logged, the instructor is PIC so legally must log it as such. The conditions of flight are IMC and IFR, therefore the flight must be logged as such.
Going by BEagle's over-emotive contribution the instructor would not log any time for a competent student doing brush up for a flight test, for the flight before first solo or first solo navigation (where I was taught never to touch the controls or give much advice if the student was handling the trip competently), let alone for a check flight or revision flight for a qualified student. Certainly anyone logging the time as flight by instruments is not indulging himself with "Parker ballpen" hours!