With all due respect to your expertise in this matter,I strongly disagree.
1.Sure,stance and protecting your chin with hands and keeping it in is crucial,but if you are fighting anybody good (why bother otherwise? ),you need any advantage you can get.
He is gonna bomb your head from all angles and you are gonna get hit.With strong neck,you ll ride /absorb those punches (accumulative effect of those ) much better.
2.strong neck improves movement of the head= the quick ,small jerking head movement while evading punches/kicks are primarily done via neck muscles
3.essential part of kickboxing/boxing is clinch=strong neck to push through to positon you where you need to be to hit /evade when your arms are tied up with your opponent is very nice advantage
4.sometimes your oponent will play dirty,trying to control your head with arms,strong neck will make that harder
5.lets not forget the intimidation factor of big neck or more importantly when your oponent realise after furious exchange of punches that you can have stronger chin