Pete Brown wrote:
If a conventional aircraft is in stable level flight and the stick is
pulled back, all of the texts I have read indicate that the aircraft
pitches up, rotating through the CG.

Is this exactly correct or is it a very useful approximation good for
all practical purposes?

I believe that is technically correct - external forces will either rotate
an object about its center of gravity and/or cause translational movement
of the object's center of gravity. But from a frame of reference relative
to the earth an object can be made to appear to rotate around any point
inside (or outside) that object.

The complication is that, unlike the idealized case of a body in a vacuum
in free fall, an aircraft in the earth's atmosphere shouldn't generally be
treated as an isolated system and the earth and its atmosphere treated as
an immobile frame of reference.