What about strongly retrofocus lenses? For example, I have a 20/2.8 designed for a 35mm SLR and it exhibits very little falloff despite covering about 95 degrees. Assuming they have the strongly-negative front element (one less cos) and a rear node that's about as far from the film as a film-diagonal, would I be right in guessing that these have closer to cos^2(phi)*cos(phi/k) falloff, where k is the pupil ratio?

If so, is there any particular reason other than cost that we don't see such lenses being manufactured and sold for large format? There are tele lenses sold for LF that mean you can use a shorter bellows, why not retrofocus lenses that allow you to go stupidly-wide without recessed lens plates and centre filters?

Is it that smaller formats tend to have much larger exit pupils compared to the film size than larger formats, which further reduces the falloff? And that we wouldn't get that benefit with LF?