Mann loves oppositional framing. He's always loved oppositional framing. In Manhunter, he used diagonal lines throughout to keep characters in visual opposition -- Crawford and Graham occupy opposing diagonal lines when they're talking in the hotel late in the film, because Crawford can't follow Graham's journey of understanding with The Tooth Fairy. Yet when Graham talks to Lecktor on the phone, where he gains the understanding, the two end up occupying parallel diagonals. All of that was achieved primarily through cutting.
And yet that movie has plenty of other scenes with the two actors on camera together in the same frame.
Again if you re-read my underlined part about not dealing with the conspiracy theory of "they weren't on the set together"...well let me reiterate it for you again.
I am not trying to convince you (or anyone else) they were on the set at the same time. The great thing about conspiracy theories is their self-reinforcing nature.
I don't really care about the conspiracy theory. I don't know whether the actors were on set together or not. Either they weren't, and Mann had no choice but to film them separately - or they were, and he made a poor directorial decision that undercut the effectiveness of the scene (IMO).
With regards to your second statement about the anamorphic lens, again filming something from the side to get both actors into frame would have robbed you of the fine nuance detail of their performance either saying their lines, or reacting to the others' lines, that only a direct-on face shot can provide.
That's your opinion. I have a different opinion. I'm not saying the entire scene should have been filmed in wide shots, but I do think a couple shots of the actors reacting against one another on camera at the same time would have added a lot to the dynamic tension of the scene.
The way the movie is now begs for viewers to question Mann's filming choices - which is exactly what happened. If he'd put in even one single shot of the actors together, nobody would have questioned it and we wouldn't be having this discussion two decades later.
Also that one shot of Clarice running back has no analog in the Heat scene.
So he could have added one.
So there's never an occasion to have that shot, as well as an establishing shot of the two of them walking into the diner. It would have ruined the smash cut pacing I mentioned in a previous post.
Mann's a smart guy. I'm sure he could have figured out a way to get the two actors on camera together and make it work.
You act like shooting the scene entirely in over-the-shoulder shots is the one and only way this scene could ever have possibly worked. No, I'm sorry, that's false.