Usually, yes. But now some[one|thing] will have to do the monitoring and gradually ramp up traffic, rollback, etc.

It's perfectly ok to immediately flip the entire traffic if you are a one man shop and your customers will tolerate it.

I've never heard that the gradual moving of traffic was a requirement for B-G deployment (though it is helpful), just that you 'flip a switch' between one running server and another one.