Here is a two-pot of the same width: one high, the other low. Which one is bigger?
In which of these pots, you can pour more fluid?
Many, probably without thinking, I would say that the high pot bigger low. If you, however, began to pour the liquid in a tall pot, you could pour it only to the level of the apertures of the spout on the water starts to pour. As well as holes of the nose in both pots at the same height, the low the pot is so big and tall with short beaks.
It is clear: in the pot and in the tube of the spout, as in all communicating vessels, the liquid should be at the same level, despite the fact that the liquid in the spout weighs much less than in the rest of the pot. If the nose is not high enough, you will not pour a pot full of water will spill out, Usually the nose gets even above the brim of the pot, that the vessel was slightly tilted, not pouring out the contents.