Assuming that's true, private companies contracted by the government may not be under that same requirement (think military specs and designs). The output as a whole may be public domain (I know what an F22 is, and the parts to build one, but the specs to those parts are proprietary) but the operations, and binaries,(specs and requirements to build the individual pieces) to produce that output may remain private.

Public domain just means it can't be copyrighted. It doesn't necessarily mean it has to be distributed to the public.

you mean like NSA toolkits?