Regarding the use of passive, why do we need to set it to true?

Queues and exchanges can be declared “passively”. A passive declare simply checks that the entity with the provided name exists.
If it does, the operation is a no-op. For queues, successful passive declares will return the same information as non-passive ones, namely, the number of consumers and messages in a ready state in the queue. If the entity does not exist, the operation fails with a channel-level exception. The channel cannot be used after that; a new channel should be opened. It is common to use one-off (temporary) channels for passive declarations. Declaring the queue as passive therefore helps to avert redundant use of resources.