I understand the principal you're describing and think it makes sense, but only if the spout is offering some resistance to the volume coming into the base. At the flow rates we're pouring at, the water is coming out slowly enough that IMHO having the wider base won't matter.
The narrowing of the neck diameter creates the resistance. The neat thing about friction & resistance is that it doesn't take a big change to have a big result. The only difference in breath control for a vocalist is the narrowing of the throat. For an instrumentalist, the throat, mouth, and the embouchure (mouth opening) are narrower. Even for a big bore horn like a tuba, the elements are the same as for a flute.