I went through the movies in my IQ yesterday (about 60) and a little over half of them were 1.78:1. Some of those must have been shot in that AR but certainly some of them weren't.
It's possible that some were shot "open matte"; shot 1.78:1 framed for a 2.35:1 window in the center to which it's cropped on theatrical presentation. I know of several films like that: Man on Fire
(2004), Schindler's List
, Top Gun
, Once Upon a Time in Mexico
, etc. When films like this are presented in 1.78:1 you see the entire 2.35:1 picture plus more at the top and bottom so no "pan and scan" editing is necessary. Of course, the director framed the shots for the 2.35:1 view; although nothing is omitted, you're not seeing it exactly as intended. In some rare instances they're not as careful as they should have been about what's in the areas outside of the wider frame and things that shouldn't
be seen are revealed, like bits of wires and boom mics. A famous instance of this is a scene from A Fish Called Wanda
wherein some characters have walked in on a naked John Cleese but in the presentation without the mattes you can see that he's wearing shorts
(you can see that here
--it was shot open matte 1.33:1 cropped 1.85:1, which can just as easily be cropped 1.78:1 without loss).