I would agree with you, but I think that to encourage any gene that impacts the health & survival of the animal is just obviously the wrong direction to go. Which is why these animals evolved with scales in the first place, eh? A bad trait is a bad trait, no matter the amount, & what's more important to protect than a creatures head, anyway? Can't survive with brain damage, or eye damage, or problems eating...if anything needs scales, a snake's head does.
Again- if having no scales on their head was somehow an advantage, snakes would have evolved that way- like the way turkey vultures evolved without feathers on their heads, so that they stay cleaner when scavenging carrion. But that has no possible advantage for snakes whatsoever. In fact, when they grab their prey, & the prey fights back with either teeth or claws, what's going to happen to the snake's unprotected head?Keeping a bad trait, no matter how minimal, is never good for the animals, which is why natural selection weeds them out.