Maris, unbelievably accurate assessment; Andy Warhol RIP.
My experience with Polaroid comes from the other end of the process. Running the processing lab (Dip N Dunk) and continually being asked to emulate the Polaroid reflective viewing experience with an E6 tranny on the light box, which was sometimes quite exasperating.
I never gave it a second thought as to why Marcus would require proof of his exposure regime, until you mentioned it. Then I remembered the set-up and noted that his bellows were fairly extended, maybe he just isn't too sure about the factor needing to be added. He also had a fair bit of front rise and I don't think the standards were parallel, which may explain why the models feet were as soft as they were.
The other aspect is to elaborate for viewers unfamiliar with using a camera without an inbuilt light meter, let alone one making adjustments as it measures the light coming off the film on the fly...
Regardless, his last picture with just the face, was very good and smacks of full extension, and as he mentioned, possibly getting an extra bit of extension from the film pack being about 15mm further back. I'm sure the Instax helped with getting exposure bang on there. I'm assuming that picture was a scan of the Instax print, which was then manipulated heavily to get the very pleasing end result.