Targeting isn't a foul reserved for helmet-to-helmet hits, and it's also not reserved for hits that originate with the "crown" of the helmet (which is the top/front area). Players are also guilty if they make any kind of forcible contact to the head or neck of a defenseless opponent. Here's an example that checks lots of these boxes.
Arkansas defensive back De'Andre Coley charges into Texas A&M receiver Speedy Noil after an incomplete pass. Coley hits Noil helmet-to-helmet, even though it's not frontal helmet-to-helmet. Officials on the field called targeting, and replay watchers upheld it. Coley was disqualified.
Let's go to the rulebook.
Here's something about targeting:
No player shall target and make forcible contact to the head or neck area of a defenseless opponent
So, not great. Coley looks like he's doing this, whether he locked in on the head deliberately or not. You could fairly make the case that Coley lowers himself to square up to make a hit and only thrusts his head into the receiver's by accident, but officials are instructed to call targeting when such questions arise.
One of the NCAA's "indicators" for a targeting foul is "leading with helmet, shoulder, forearm, fist, hand or elbow to attack with forcible contact at the head or neck area." Coley leads with his helmet and hits the receiver in the head.
This is at least the second example in two nights of an officiating crew seeing targeting and calling it exactly right. Coley might not have meant this, and I have no reason to think he's a dirty player. But this is why targeting exists.