Avmervo,
I agree, you are correct about the intake.
But it kind of is not moot to discuss square bore anything, as Tom states in his OP he is using an Edelbrock square bore carb not a spread bore Q-jet. Thus the need to use an adapter.
It's just that someone got it backwards as to which was square bore and which was spread bore.
Now as you say spread bore carbs, such as the quadrajet, have big secondary bores and smaller primary bores. The bores, front to back, of the Quadrajet are on the same centerline. The center of the back bore is in line with the center of the front bore, the distance between the front bores is spread to line the centers with the rear bores, thus spread bore. If the carb is a square bore and the manifold is a spread bore an adapter is used to flow the air/fuel from one type to the other. A conduit from one hole size and location to another of different size and location.
Of course I could be wrong.