Langner’s final Stuxnet analysis comes with surprises

On a government project? Never.

To me it sounded more like they were keeping the malware quiet so that it could spread sufficiently before getting aggressive once it was plausible that it had made it into the centrifuge facility, at which point, it no longer needed to be stealthy.

That's not what the report claims at all.

It claims that they may have wanted Stuxnet to be exposed, for boasting/deterrence. It also claims that they likely lost access to the internal network, and needed more virus-like behavior in order to spread to the right computers. Virus-like behaviors that raise suspicion and make it discoverable.