My thoughts and experience as well, moreover when I did my JAR multi-conversion on the Duchess, mixture cuts were mandated as verboten, the reason being as outlined in previous threads. I'm not saying don't practise/demonstrate it, but give yourself enough altitude to recover if it's screwed up.
All my multi piston s/e work was based around setting zero thrust.
Like all things in flying there are different points of view based upon personal experience. But in a court case for instance,the legal eagles would quickly seize on such recommendations taken from Lycoming Flyer magazine (2002 issue) - edited extracts. Page 49 under the heading
NTSB Warning On Simulated Engine-Out Maneuvers.
Quote: "The fatal crash of a light twin in which a flight instructor and an applicant for a multi-engine rating were killed prompted the NTSB to issue an urgent warning to all pilots simulating an engine-out condition on multi-engine airplanes. The Board's investigation revealed that some flight instructors do use the fuel selector or the mixture control to shut down an engine to test a multi-engine applicant. Although this is a recommended procedure, the urgent warning was aimed at flight instructors who were using this procedure at altitudes too low for continued safe flight. The NTSB observed that use of such procedures at traffic pattern altitudes may not permit instructors enough time to overcome possible errors on the part of the applicant.
The recommendation by the NTSB means that all simulated engine-out operation at the lower altitudes should be accomplished by retarding the throttle and this should be done slowly and carefully to avoid engine damage of failure. The current technique will protect the engine
and at the same time provide for instant power if it is needed." Unquote.
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Personal comment only: The subject has been discussed numerous times in Pprune with good arguments for and against mixture cuts. The problem has always been the startled and possibly unpredictable reaction by students and this can happen equally with a throttle or mixture closure. One could argue that if it is safe to cut the mixture at low level to simulate an engine failure on a light twin, then why not do the same with a light single at say 500 feet agl after take off during ab-initio training as practice engine failure followed by a simulated forced landing glide?
After all, in all cases the instructor is counting on the engine to successfully restart when he opens the mixture control to rich and opens the closed throttle.
Few sane instructors will deliberately cut the mixture to simulate a low level engine failure in a single engine type simply because of the fear (risk) the engine may not pick up after the mixture is set to rich. That is a reasonable precaution. Same then with a twin because if the engine fails to pick up quickly after the mixture is returned to rich in a twin, then things quickly get serious with the inevitable loss of airspeed associated with a windmilling (not feathered) prop. Perhaps that is one reason for the NTSB recommendation of "The current technique will protect the engine
and at the same time provide for instant power if it is needed."