"The alternator loads the engine the same amount whether the car uses the curent generated or not."
No way! The power consumed from the engine by the alternator is in proportion to the square of the current produced! You cannot compare it to a clutched, relatively constant power consumer such as the a/c compressor. The alternator will only produce the current demanded of it by the electrical system at the moment. Its current rating is a MAX available, and that only above a specified rpm. On a cool day when the only consumer is the ECU and ignition, injection components, the alternator will produce very little current.
'91 MB 190E 2.3
'08 RAV4 Ltd 3.5
'83 Lazy Daze m'home 5.7