> Nolan could have shot it on anything he wanted, and he chose the less convenient way, because that is his process.

Kinda. There are also interesting technical reasons. From my lay person understanding:

  1. IMAX film is physically larger and creates a higher quality image
  2. Because of the size and machine noise close up dialog is normally redubbed.
  3. Nolan (and team?) came up with a method of sealing off the cameras' noise that made them even larger, so they had a system of mirrors that allowed the actors to interact in a more natural way and allowed close in capture by IMAX with integrated sound.

The system of mirrors reminds me of Errol Morris' Interrotron which allowed him to film an interviewee's face directly from the perspective of the interviewer.

https://en.wikipedia.org/wiki/Interrotron