Isn't that negated by Trump, the aggrieved party, attaching to Texas?
Trump was not a party to the original complaint. In part, I believe it would not have been state v state if he was a party. He, like other states that have filed to intervene, has to wait for SCOTUS to decide if the case will be heard or denied. If accepted, then the courts decide who gets to intervene.
The way I understand it is the court will first need to determine if this is indeed a state v state matter, and if there are no other possible venues in which it can be heard. If there are other venues, the exclusive original jurisdiction would not apply, and the case would be denied.