61.51 doesn't specifically mention approaches. All it says is that CFII's may log instrument time while instructing.

My interpretation of 61.57 is that you may not log the approaches unless you actually fly them.

(c) Instrument experience. Except as provided in paragraph (e) of this section, no person may act as pilot in command under IFR or in weather conditions less than the minimums prescribed for VFR, unless within the preceding 6 calendar months, that person has:
(1) For the purpose of obtaining instrument experience in an aircraft (other than a glider), performed and logged under actual or simulated instrument conditions, either in flight in the appropriate category of aircraft for the instrument privileges sought or in a flight simulator or flight training device that is representative of the aircraft category for the instrument privileges sought—
(i) At least six instrument approaches;
(ii) Holding procedures; and
(iii) Intercepting and tracking courses through the use of navigation systems.

Performed being the key word.