Interestingly the questioners, in this case the Senators, are not under oath and they can say whatever they’d like. Regardless of how false or nonsensical.
At the last hearing, for instance, Jack Dorsey said that they do not shadow ban, but later pictures appeared of their administrative interface and certainly that capacity was there. An outright lie and yet he isn't even interrogated on this. Wouldn't there be arrests and trials if it truly was a federal crime?
Look at the prosecution of Roger Clemens. Why the hell was Congress holding hearings about steroid use in baseball?
https://www.nbcnews.com/politics/congress/5-people-who-lied-...
That parallels to attorneys in a trial. Although in a trial there are some limits to questions that can be asked. In a Congressional hearing, the witnesses don't have anyone who can specifically raise an objection on their behalf, they just have to wind down the clock.
Honestly, most of these hearings would be better conducted via letters. Then you wouldn't get nearly so many "I would have to get back to you" answers, often without serious followup.