I'm not so sure about that. The committee said there was another witness who corroborated it. But they didn't name the witness, and the witness wasn't responding to Hutchinson’s live testimony, so not all that convincing. From their report...
After he exited the stage, President Trump entered the Presidential SUV and forcefully expressed his intention that Bobby Engel, the head of his Secret Service detail, direct the motorcade to the Capitol. The Committee has now obtained evidence from several sources about a “furious interaction” in the SUV. The vast majority of witnesses who have testified before the Select Committee about this topic, including multiple members of the Secret Service, a member of the Metropolitan police, and national security and military officials in the White House, described President Trump’s behavior as “irate,” “furious,” “insistent,” “profane” and “heated.” Hutchinson heard about the exchange second-hand and related what she heard in our June 28, 2022, hearing from Ornato (as did another witness, a White House employee with national security responsibilities, who shared that Ornato also recounted to him President Trump’s “irate” behavior in the Presidential vehicle). Other members of the White House staff and Secret Service also heard about the exchange after the fact. The White House employee with national security responsibilities gave this testimony:
Committee Staff: But it sounds like you recall some rumor or some discussion around the West Wing about the President’s anger about being told that he couldn’t go to the Capitol. Is that right?
Employee: So Mr. Ornato said that he was angry that he couldn’t go right away. In the days following that, I do remember, you know, again, hearing again how angry the President was when, you know, they were in the limo. But beyond specifics of that, that's pretty much the extent of the cooler talk.⁴⁴⁹
449. For security reasons, the Select Committee is not releasing the name of this employee. Select Committee to Investigate the January 6th Attack on the United States Capitol, Transcribed Interview of White House employee with national security responsibilities, (July 19, 2022) at p. 73. See also Chapter 7, which discusses this topic in greater detail.