The short version is that the Supreme Court has agreed to dilute its original jurisdiction, through a series of cases that lack coherency.
In Marbury v. Madison, SCOTUS held that it was powerless to expand its original jurisdiction beyond what the constitution recites - as between the constitution and Congress, the constitution must control. This "rule" is obviously discarded when it is convenient to do so.
I note from your link:
But where claims are of sufficient “seriousness and dignity,” in which resolution by the judiciary is of substantial concern, the Court will hear them
As I pointed out....what does it take? This case is about the most serious thing to come out of Arizona since Miranda...and to me, goes way beyond that little procedural dustup.
This is about the existence of the nation. Do we have borders, or is Invasion a civil right?
Did the 1846 War and the Gadsden Purchase mean anything, or was I born on Mexican Territory, and will I have to show my passport to see my Mother's grave?
It's that serious, folks.