why does my holley 94 have two barrels, two butterflies?

[hueyhoolihan]

all my research shows that both barrels of a holley 94 (1941 ford oem carb) open at the same time, at the same rate, and have the same sized jets and feed into the same large common area inside the intake manifold.

so what makes one a "primary" barrel and the other one a "secondary", as they are often described? and, if queried about the difference between the two barrels i've been given hints that they open at different rates, which would make sense, if they did...but they don't.