The point here is that a runtime panic is not an exploitable event - at the very worst, it's a DoS as it usually results in the program exiting. AFL isn't even

The point here is that a runtime panic is not an exploitable event - at the very worst, it's a DoS as it usually results in the program exiting. AFL isn't even nearly guaranteed to catch everything, but what it's shown here is that the program contained bugs which would've resulted in an exploitable event in C. The program probably contains more bugs, but following this pattern, it's more likely that they result in panics in most of the worst cases, not exploitable events.