The reason of Standby power in the 1st place is for Emergency use when u loose all sources of AC power,so u remain with DC power that'll last for 30 minutes if u use a single battery.Standby Power on AUTO only works if BATT switch is ON otherwise place the Standby Power switch on BATT but the switch Hot Batt is OFF.
As for the disconnect relay at Glide slope capture is to prevent in case of a faulty DC bus to affect the other,it"s a safety aspect