Still on track. Don't think of it as 'constraining' the system - you are just applying two forces. If you like, think of a broom stick floating in orbit. Two sky rockets attached, pointing in opposite directions - and you can slide them to any position. You can always choose positions in which, when you fire the rockets, the broomstick will rotate around a point which isn't the centre of mass. (Which is the point of the thought experiment - that an object isn't magically constrained to rotate around the centre of mass when affected by external forces.)
Beacause an aircraft has a tailplane at one end, and the wing lift (the largest force being applied) is close to the centre of mass (call it the second largest force - although it depends on what the aircraft is doing), then the centre of rotation is very close to the CofM - so it is easy (although not technically correct) to say the two are the same.