Not sure about the Harley ECM but automobile ECM's have had adaptive memory for years. Disconnecting the battery clears the adaptive. Ford for example many times won't idle after a battery is disconnected or goes dead. The buildup in the throttle body restricts air past the blade but the ECM has compensated over time. The throttle body has to be cleaned to restore idle. I would wager the Harley also has adaptive memory. Disconnecting the battery won't affect mapping or programming. Just the adaptive.
