The Back To The Future trilogy was filmed this same way. I have both Fullscreen & Widescreen copies of the films. You see more at the top and bottom with Fullscreen versions.
This partly led to the famous DVD Framing Fiasco with the first Widescreen release. Someone did something wrong, and the Mattes were not placed in the correct place.
I am not sure why ANY films are shot in 1.33:1, when the intended theatrical releases are going to be 1.85:1... Especially back in 1985.
At least all of the special effects for the BTTF films were done on 1.33:1, before they added the mattes.
What gets me even more confused, I have a DVD movie where it has both versions on the disc, and they don't match up to the negative at all. The Widescreen version has more image on the sides, than the fullscreen, and the Fullscreen version, has more image on the top and bottom that the widescreen. I took two screen captures on my computer and overlaid them, and it is clear that the negative has more to see than my overlay. It looks like four corners are missing from the overlay!
I wish all movies had one standard. It would make things easier for everyone. I get tired of hearing people complain about "Black Bars", because all of the confusing "Tech" variations.