Where did Pe make that statement?

Aiming point refers to the location a hand held heat gun should be directed to, with is really more applicable to RC cars, not airplanes. The use of a heat gun with RC aircraft for establishing engine temps is not recommended because it provides zero information relating to what temp an engine is operating at during various stages of a flight. An up line runs hotter than a down line. A landing approach runs cooler than any other phase of flight, while a taxi back can run only slightly warmer than the approach phase, but substantially cooler than an upline or vertical oriented phase of 3d flight. Tumbles, hammerheads, tail slides, and torque rolls cause and engine to run quite hot. The temperature delta between one phase of flight and another can be upwards of ~150C. In a poorly tuned and/or cooled engine that delta can be much more, and more than enough to destroy an engine in one flight.

So for RC airplanes a temp gun is quite literally...useless.