My thoughts exactly--

If a 375H&H Double could shoot 1.5 MOA out to 250-300 yds with a qd scope I think it would be a go to option vs a bolt as a 2nd DG safari gun(Primary gun- heavy Double).
You could get aimed on target with the 2nd shot faster if needed and still have the advantages of a Double if things got close range sticky suddenly and you were carrying the "wrong" gun.

So yes, I would much rather carry a Double 375 as b/u( assuming it accurate at distance) on Safari than a 375 bolt anyday!