Single throat with 66mm bore?

Or progressive with 34mm primary and 52mm secondary?

How do you calculate surface area? pi x radius squared?

So the area of the 66mm bore is: 3,419sq mm?

34mm primar:y 907sq mm

52mm secondary: 2122sq mm

total: 3029sq mm

I assumed the combination of the two smaller bores would have more area than the single 66mm bore, but the math says otherwise!