Freddy opens his mouth, then closes it again in that way which silently speaks of biting one's tongue and trying not to apologize right after being told not to apologize. Then he shakes his head with a sigh and slides the rest of the way down to his rear.
"Ain't talkin'," he mumbles, mostly into his knees. "Well, I mean, it tries to, I guess, but..." A shrug expresses many things but mostly the fact that attempts to communicate don't do a whole lot of good when they seem to be vocalized on an entirely separate plane from the one inhabited by the person with whom one is attempting to communicate.
Yes, a shrug just expressed all of that.
Look, he's tired. Words are hard. If he could just, like, beam these facts into Caleb's head right now, he so would.