From the article

And this has to be at the White House specifically because location determines oversight. When infrastructure is part of the Executive Office of the President, when it exists at 1600 Pennsylvania Avenue, it can be classified under executive privilege. The East Wing sits directly above the Presidential Emergency Operations Center, the bunker where Dick Cheney sheltered during September 11th. By demolishing the entire East Wing, you create space to expand that existing secure facility, integrate new infrastructure, go deeper underground. All protected by the classification that covers anything related to presidential security.