Shooting on any FF body is totally missing the point. What in the world are you getting at?
Regardless of what you are thinking, the "not a full frame sensor" in the phone is kind of the point. As well as all of the "AI" processing done to the photons captured by whatever piece of glass is in front of it. It's this processing that makes the phone they are showcasing different than an "modern FF body" that you are suggesting.
The iPhone in this use case has multiple limitations that make no sense in the use case where it is a glorified sensor.
You can't swap the memory out, the memory is limited to begin with, you can't use attachments like monitors and other gear, etc.
If you're going to end up renting a huge professional rig to attach a sensor to it to get the same results as a typical FF or even APS-C camera, you've lost the message.
In other words, "that rig is so big yet comes with so many limitations that it's foolish to not just use any normal camera body"
The point is that it is the internal recording that is being touted. It captures log. It captures ProRes. Even without the special lens, it still does all of that. To show that off, they put a really nice piece of glass in front of it. Even if they disable all of the AI processing, it's still really clean video.
Today, what is a normal camera body? BlackMagic's cinema cameras are not much larger than an iPhone Pro Max Ultra+ model. I have seen the BMD 16mm format camera with giant Angénieux lenses attached to them. The camera is barely noticeable. Not really sure what you're point about the camera size is, and why you're so focused on it. The fact that a small device like a phone can create the clean log ProRes file is the point.
Regardless of what you are thinking, the "not a full frame sensor" in the phone is kind of the point. As well as all of the "AI" processing done to the photons captured by whatever piece of glass is in front of it. It's this processing that makes the phone they are showcasing different than an "modern FF body" that you are suggesting.
You've clearly missed the point