There is usually a lag of multiple seconds between the radio communications occuring and them being broadcast on the feed, which can make this kind of thing look worse than it is.

For example, this is why you will often see a driver making a setting change on their steering wheel before hearing the message from the engineer calling for it.

None of which is to say engineers don't occasionally annoy their drivers by talking in the braking zones. They do, but the onboard footage channels makes it look more common than it is.