Why Wasn’t United States v. Arizona Filed in the Supreme Court from the Outset?

Volokh Conspiracy "1. A federal statute, 28 U.S.C. § 1251, provides that:"

(a) The Supreme Court shall have original and exclusive jurisdiction of all controversies between two or more States.
(b) The Supreme Court shall have original but not exclusive jurisdiction of:
(1) All actions or proceedings to which ambassadors, other public ministers, consuls, or vice consuls of foreign states are parties;
(2) All controversies between the United States and a State; (Emphasis added)
(3) All actions or proceedings by a State against the citizens of another State or against aliens.

In other words, the US did not have to go through lower courts first. That's significant, but I don't know why.