Three fragmentary copies can’t establish that Kings lines up with the later text. Isn’t that agreement from silence?

Fair. The fragments agree with the Masoretic tradition where they overlap, and the coverage is limited; that is all that can be said. Kings also has a well-known chronological divergence between the Masoretic and Septuagint traditions that the Qumran fragments are too small to settle. The honest summary is present, fragmentary, and consistent where checkable.