Given the nature of the toxic tribal environment surrounding current U.S. politics, it is critical for John Durham to protect his mission from even the appearance of impropriety. One can easily imagine how everyone in/around the purposefully tight group would demand utmost confidence and security with any aspect of their investigation.
Certainly if a special prosecutor like John Durham was to receive critical material to assembly a political “Little Boy”, anyone in/around the delivery process would be required to go completely silent thereafter. It is the only safe way to ensure the objective.
So after months and months of whining and complaining that Barr/Durham aren't leaking to him on his timetable, Sundance is defending Durham going totally silent. He now gets it that Durham can't leak without jeopardizing the mission. It's "critical" for a "purposefully tight group" to "go completely silent." It's "the only safe way."