Yes when the fear/block is strong enough in a surprise scenario, the technique may not work then and there, but that doesn't mean it will fail a second or third time, once you know what you're up against. I can attest to this, as the techniques have and continue to work for me, while blocking has reached a point where it's far and thin. Additionally, using the techniques proactively in a deliberate manner where you're not afraid to show yourself as someone overcoming a stutter can prove valuable.