Remember that the turn "co-ordinator" is calibrated for a specific speed and only shows rate 1 if you have 1g, ball in the middle and this speed. However, for the IMC rating simply peg rate 1 and fly in balance.
Are you sure about that DFC? Reason I question it is when I'm doing climbing rate one turns at 80knots and the co-ordinator is aligned for rate one the AH shows about 12 degrees of bank. Repeat at 100knots and it shows about 17 degrees (like it should). From this observation it would appear that the turn co-ordinator is indeed aware of the speed of the aircraft.