“Sure it does. Article I, Section 9 gives Congress exclusive legislative control over the district. They could carve it up and do what they want with the remainder.”
NO it does not. Legislative control is one concept. Giving a few acres statehood, that would change the entire nation, is an entirely different concept that goes far beyond any understanding of legislative control. The district was carved out of other states’ territory by the Constitution. Makes about as much sense as someone claiming the Bill of Rights were subject to Congressional legislative control.
But nothing in the Constitution explicitly prevents Congress from doing that. It'll be for the courts to decide, assuming it makes it through the Senate in the first place.