if you got a big enough hole to fill, the booster type doesn't mean as much re airflow potential

I agree, it's the smaller primary venturis that are significantly obscured (lower CFM per square inch) by annulars, it evens out as the area goes up.
Why doesn't someone make s m a l l e r annulars? The usual stuff is cast, which requires wall thickness and internal strength at the cheapest cost.
Not enough sales volume. 3-D printing?

Shameless self-promotion: I "invented" adapting a Holley 4010 annular secondary booster to the 1933 Harley-Davidson 1 bbl. side-draft carb (Linkert Model M) used for 30 years.

http://www.victorylibrary.com/L-BK.htm