Exactly, they were off-camera.
I have a weird feeling this is real. I'm an oldfag. I remember when TV looked like this, literally, it's as familiar as can be. If it is fake, it was done by someone incredibly talented and detail oriented. The authenticity is stunning. I don't see someone creating this for promotional reasons. That kind of bad taste would only draw criticism, as they'd undoubtedly get caught.
I actually think this is a decayed video recording of an original kinescope. See definition below.https://en.wikipedia.org/wiki/Kinescope
In other words someone video'd this off an old kinescope of the shooting footage. Hoarded it, finally someone else got ahold of the old tape and uploaded it. The kinescope would've been taken from the original footage--clandestinely no doubt--before it was destroyed. That kinescope might still be out there. It would be better quality though, due to expense, whoever made it would have shot it on black and white film.
I've seen old, deteriorated professional standard video played back in recent years. (A friend of mine works at a TV station and had brought, well, sneaked, some old shit home to play it. He collected old school audio tapes, too, and old film and TV and sound equipment. He helped me transfer some reel-to-reel recordings of my late Dad reading Shakespeare onto digital media.) This is totally consistent with how that stuff looked.
Check this out: https://www.youtube.com/watch?v=fBi1OK99swU
At about 7 minutes 41 seconds there's a shot of the set minutes after she killed herself, with a coworker presumably looking down at her body behind the desk. It's identical to what we see here. Also, if you watch the whole thing, there's a brief sequence of the real Christine interviewing someone on air. Her real voice sounds like the voice on this recording, albeit with the distortion it's hard to be sure. But it's not inconsistent at all.
This is so sad.