The US government does not have a position. (Not even sure what that would mean other than maybe the White House proclaiming?) Various federal agencies, departments and offices have supported various theories including lab leak, and some have changed their leading theory over time. The document you cite would also not be a government position, it’s a summary of a hearing that may one day be included in a report. You need to cite one of the various reports from the federal government in support of a lab leak.