It may even be that the committee already has corroborating testimony but has to hold it close to the vest for now.
But to be honest with you, that small portion seems like a tempest in a teapot and just another distraction from the main theme.
Trump knew the crowd was armed and pointed them at the Capitol without regard to anything.
That implies, at best, complete disregard for the safety of those in the Capitol, and at worst intent to harm those in the Capitol.
Given his later actions after being told the situation was bad enough that the crowd inside the Capitol was shouting for Pence to be hanged and he tweeted his grievance with Pence instead of taking steps to calm the situation his intent is clear as day.