If the point is to abort, you can't rely on the engines being throttled down to the accel limit -- you have to be able to successfully get out of any reasonable

If the point is to abort, you can't rely on the engines being throttled down to the accel limit -- you have to be able to successfully get out of any reasonable scenario and the engines running away does not seem unreasonable. (I don't know exactly what the abort requirements are, but the point is just that it's not easy.) Also, during an abort scenario, the aero drag is pushing Dragon back onto the launch vehicle, so you actually need more thrust to overcome that, too. (Although that obviously depends very strongly on the dynamic pressure at which you abort.)