Hey, Jon.
Yeah, you’ve nailed the illustrative and cosmetic reasons for inserting B. The bottom line is when it feels right and enhances the piece rather than distracting.
You mentioned ‘The Speaker’. Are you asking about cutaways in a narrative or documentary?
In a Doc clarity generally tops the list. So B should be inserted just as you said.
Narratives offer a lot more flavor due to Diegesis – simply the telling of a story by a narrator. Parts of a film can either be diegetic or non-diegetic. Mostly applying to sound, it can also apply to inserts that depict something that is not taking place in the world of the film (a non-diegetic insert). Titles, subtitles, and voice-over narration (with some exceptions) are also non-diegetic.
Here’s an example: In “The Truman Show,” while Truman sleeps soothing music plays, as is common in such scenes. However, after cutting to the control room, we see that the mood music is being played by Philip Glass standing at a bank of keyboards. The shift is from apparently non-diegetic to diegetic, and is a joke.
Whew! Aren’t you glad you asked?