Yes, I've noticed that. It's hard to miss really.
I assume it is, exactly as you say, virtue signaling.
Virtue signaling isn't just an end in itself. It's often (generally?) a feedback loop - the person is not just trying to demonstrate that they're virtuous, but to reassure themselves that the standards upon which they're measuring their nominal virtue are legitimate.
So calling for ever more draconian punishment is not so much the point - more, the point is to call for draconian punishment, then have somebody else applaud and even amplify that call. That helps to solidify the sense of moral superiority since it's not just that I believe that I'm morally superior because [X], but other people do as well. We all agree that this is the morally superior position, so we must be right.
But underneath it all, what it really is is just foul, vindictive, hateful assholes who enjoy the thought of people suffering, and try to excuse it with the belief that, by whatever standard, this person deserves it.
Though they'd be the last to admit it, the nominal crime isn't the point. They just get off on the suffering of others, and the nominal crime is just an excuse.
And since their whole position is a lie - because their real motivation is just a sick pleasure in the suffering of others and their moral posturing is just cover for their loathsomeness - they need constant feedback to convince themselves that they're in the right. And conveniently enough, there are plenty of other people in the same situation, so they can, and do, reassure each other.