Yeah it’s real & one way where you can get continuity errors. I had a friend who’s job it was to carefully catalog all set objects in FileMaker Pro so he could reconstruct the parts of set that had to be torn down when moving cameras, lights, etc.
Famously, Anthony Hopkins and Jodie Foster barely did any direct interaction during the filming of The Silence of the Lambs. Hopkins was essentially walled into his prison cell during filming that took place in the "prison", so they did all his shots for as long as his bladder could last before breaking the set down to let him out.
I don't know for sure that this is the one that I watched, but I think so and the time frame is about right: [The Inside Story](https://www.imdb.com/title/tt1918873/).
The deep details of the movie are fascinating. Schlock filmmaker gets a recent Oscar winner and an experienced but little-known in Hollywood actor to take on a very confusing story, which then debuts into a slow burn that gradually builds over more than a month to become one of the best movies ever? You would never sell that as a script because nobody would believe it, but it really is true.
In the video, it was suggested that Caine would get in the back of other actors scenes. Of course the extent of it in the video is obviously parody.
But is there anything to it? I imagine an actor could, for example, cheat a bit in the two shots; look right at the camera while they are the speaker, then just shift a little bit while the other actor is speaking, not enough to be obvious, but just enough to catch the camera with a little bit more of their face…
The Director and Director of Photography would immediately reposition them. It would look very awkward.
What does happen often is impactful news will be delivered causing the foreground actor to turn to camera and contemplate as they rack focus from the background actor to the foreground. See also, a door slamming or an event happening just off camera.
It’s an easy way to get a nice little two shot of both actors faces
