NSEU,
Indeed the QRH and FCOM are always the latest and greatest but that sentence regarding QRH "IRS LEFT" msg seems to contradict the BGS arming logic.
My notes are also old, so I am at a loss as to why the the FO's/CTR IRU's can not assume "command" of the BGS system with that msg displayed.
Another of those aviation anomalies that make you go "Mmmmm...."
Rgds McHale.