It is possible that Barr is against bald faced lying. But I doubt it. He was pretty blantant about the Mueller report. Complete exoneration and all.
It is more likely that Barr knows something that has not come out yet. It is also difficult to lie about the actual laa. It is written pretty clearly. He might have been willing to argue that it was not an important law that trump fractured.
Or maybe, being on his knees sucking has made him irritable.