Tiger
John Farley's explanation can be illustrated at the other end of the speed range that you experienced - the stall warner won't go off BELOW the stall speed (which will be that for 1g flight) if the g is low. Next time you're in the Tutor look at the airspeed as you go over the top of a loop - if the speed is low, and the stall warner hasn't gone off, then check the g-meter. It'll be (well) below 1g.
You'd be surprised at the number of 4th year MEng Aeronautical Engineering undergraduates that can't grasp this on a flight test course, so you've done well to pick it up. Enjoy!