I went out and tried mine, in gear it won't start, in gear with clutch in it starts, mine is a 2012 Iron.
Wiring diagram shows as clutch switch , goes to the TSM, TSSM, HFSM module.
BK/R wire and BK wire
BK/R = Clutch Switch
BK= Chassis Ground

 

In the troubleshooting section of the Owners Manual it states :
Starter Does Not Operate or Does Not Turn Engine Over,
The #4 cause is "clutch lever not squeezed against handlebar or transmission not in neutral"