At least you have for me. Even when the dyno compares drum speed to engine RPM to figure out the final drive without input from the operator (and I fully believe the dyno does this -- it is the way I would want it!) it is still using that final drive as an input to the calculations.
You MUST KNOW that gearing to convert observed torque and HP into engine torque and HP. There is absolutely no point to the "1:1" discussion that I can see.