[Question] Why I need -b parameter to receiver

[repli2dev]

Sorry for question in issues but I miss one thing from the documentation that prevents me from finishing integration.

I have configuration:

messenger:
    buses:
        mailSenderBus:
            singleHandlerPerMessage: true
    transports:
        postgres: 'doctrine://default'
    routing:
        SendMailRequest: postgres

services:
    mailSenderBus: MailSenderBus(@messenger.mailSenderBus.bus)
    mailSenderHandler:
        class: MailSenderHandler
    doctrineTransportFactory:
        class: Symfony\Component\Messenger\Bridge\Doctrine\Transport\DoctrineTransportFactory
        tags: [messenger.transportFactory]

Messages are enqueued OK, yet when I run

bin/console messenger:consume -vvv postgres

The messages are not handed... I have to run this to make it work

bin/console messenger:consume -vvv postgres -b mailSenderBus

Why? Is that desired? The expected behaviour is that the first command should process all the messages, instead it gets to the envelope and silently discards it... which is 🤯

Thanks for clarification