I'd rather use a flashlight bezel for striking and use a knife for the blade. If you need to hit to create space and time to deploy a knife, hit with your offhand while deploying the blade.
Striking with a not so smooth part of handle or blade tang could open someone up and if a bystander/cop sees you with a knife they will assume you cut them and put the blade away. You are stating you felt your life was threatened by deploying a deadly weapon, whether you use the blade or use it as a palm stick.
For me instructors teaching to do so would be similar to firearm instructors teaching shoot for the knees, but since nobody (generally speaking) cares much about knives nobody who knows any better calls b.s. on it.