The defender needs to have the intent to "attack with forcible contact the head and neck area."
It's not like the crown of the helmet indicator (where intent is irrelevant). For this indicator, refs can and should consider other factors that are indicative of purpose.
In this case, there are plenty of factors that suggest the DB's intent was not to specifically make contact to the head or neck (WR moving his head down and into the defender as the WR turned upfield; fact that defender's head was up and came even further up through the tackle; fact that the defender wrapped up and made a form tackle as opposed to delivering a blow to the head to bring the WR down).
This rule was put in place to stop headhunting, not to penalize any and all contact to the head/neck by a defender's helmet, shoulder, arm, forearm, hand, elbow, etc. It's there to stop knockout shots to the head, not to eject players who bump foreheads or facemasks in a bang-bang sequence while making a form tackle.