(Model space set to unit length in centimeters and unit scale to 0.1)
(Camera: 50mm, with focal point locked to the same object each time)

For the exact same scene at the exact same camera view with the exact same camera settings test two scenarios:

a) switch aperture type to "radius" and set to 2cm (this corresponds to an f-stop of 50mm/20mm=2.5)

b) switch aperture type to "f-stop" and set it to 2.5 (as calculated above)

Observation:
(a) and (b) should render the same, but they do not.