Roast and publicly humiliate ? If only.
The vast majority of the proceedings where The Zuck graced committee members with His Presence was a quite polite and almost fawning affair. The amount of roasting that could be done in those conditions would require a century of constant heat in order to unfreeze a piece of toast.
I would really like to see him roasted and dragged over the coals, but to be able to do that, said committees must have a means of pressure, which they don't because what on Earth can they threaten him with ? If there are any legal entaglements, GDPR is going to take care of it and there will be no need for a committee. So, basically, The Zuck is just saving everyone's time, unpleasant as that sounds.