The "nose" was only not heated if glass is a perfect insulator. But glass is not a perfect insulator. And as-shown, a lot of that "nose" was glowing-hot after

The "nose" was only not heated if glass is a perfect insulator. But glass is not a perfect insulator. And as-shown, a lot of that "nose" was glowing-hot after being hit with the torch, and none of it was subsequently quenched in water (as Prince Rupert drops are by definition).