That was claimed by Garland but no proof has been shown. The leftist media is just repeating the claim unsubstantiated. Note however that Smith has not claimed this to Judge Canon. If it were really true, Smith would be making that claim in court and backing it up with evidence.
According to my LEO friends who work closely with the FBI, the “deadly force clause” is standard in federal court search warrants. They all concur, however, that there is nothing standard about a warrant to search the property of a former POTUS, who is surrounded by secret service agents sworn to protect the POTUS at all costs, and there is nothing standard about the AG, himself (as opposed to the United States Attorney for the district court having jurisdiction over the proceeding), signing the warrant application.