Exactly, Nev.
The confusion from some low-level pilots arises from the fact that the aircraft only knows about the air-mass it is flying in, but the pilot can't see that air-mass, and so is navigating and assessing aircraft performance by reference to the ground.
Rate of climb or descent won't change whether turning upwind or downwind.
Angle of climb (relative to the ground) will change, and this is why the low-level pilot "feels" that his aircraft is under-performing or over-performing respectively.
Radius of turn (relative to the ground) will also be affected, hence tempting the untrained to increase angle of bank turning downwind, reducing aircraft performance potentially to the point of stall, simply attempting to achieve a ground-based goal.
These matters of physics should be compulsory learning for low-level endorsements, but obviously they are not.
Perhaps we have uncovered one reason for QF mandating Year 12 for it's applicants. Although I don't know that completing Year 12 necessarily prepares one to understand the above. It should be part of the pilot training syllabus for all pilots, and particular emphasis for low-level endorsements.