It really protects the filibuster more than it protects the tax reform proposal, which has yet to be worked out. From the New York Times:
“This is the last, best chance we will have to cut taxes,” said Senator Lindsey Graham, Republican of South Carolina and a member of the Budget Committee, who warned that the consequences would be ruinous if the party failed.
“That will be the end of us as a party,” he said, “because if you’re a Republican and you don’t want to simplify the tax code and cut taxes, what good are you to anybody?”
Well, yeah. That about nails it.
Now on to negotiations with the House, which passed its budget resolution on Oct. 5.