You realize that if the Framers wanted to require a supermajority for appointments, they could have just written that in the Constitution, right? It's not like the idea of supermajority requirements were foreign to them (see: amendments, treaties).
Well you get a star for actually being familiar with the constitution, now how about you explaining that each house of congress is charged by the constitution for the establishment of their respective rules and last I read the senate rules, changes were to be made at the beginning of each congress and not midterm. But when do the commies ever really care about rules, or laws for that matter, unless they can be twisted to their advantage.
The Constitution only states that the chambers set the rules for their own proceedings. There is nothing in the Constitution that requires the chamber to keep those rules for the entirety of a session.
You are correct, it was part of the senate rules, in the end none of it really matters, the commies will do what they will do regardless of what they said when republicans were considering a similar thing. Hypocrites will be hypocrites, there should be a law.