Image circle and falloff are two different things. A pre-WWII Angulon does have the image circle, at f:64. But it has almost cos^4 falloff, and any center filter will reduce the image circle due to vignetting.
Anything Biogon-like has cos^3 falloff or close to that. Super Angulon, Grandagon, Fujinon, or others. There isn't that much difference in falloff.