I too would call it prudent (!), especially after the State Department series of debacles under the Obungler administration and in the international community.
Mueller now has him lying to the Federal Inquisition, which brings all his previous testimony under closer scrutiny.
Now the Fed will look closer at his previous statements, and now they figure that they 'own him', and will begin to squeeze him for more information, even if it is a created fantasy.
Don't forget : it was a falsely created fantasy that began the Inquisition in the first place !