404 Titan
Bottle 2 has a restrictor!
From the AOM:
"The discharge cartridge of bottle 2 comprises a flow metering system, and so fire extinguishing agent is discharged slowly into the compartment to ensure sufficient agent concentration for 120 minutes."
(Some have 240 min instead of 120 min.)
Again, if Bottle 1 inop/empty, you have no immediate fire fighting for NEITHER compartment. (Bottle 1 discharges in 60 sec).
So, "associated Compartment" like the MEL says is pure rubbish.