1. I think (and I've been known to be wrong quite a few times). The neck chewing ultimately has to do with either establishing dominance or its part if their "shake and kill" DNA.
Female Rottweiler Freyja does this all the time with my older male Catahoula/Pit Sheldon. If it goes on too long, and I hear too much rough play, I break it up. Freyja gets to be like a shark in a feeding frenzie and has hurt Sheldon a few times.
2. Since I was a kid on the farm, with Shepherd/Collie mixes, and other breeds, I have seen dogs chew sticks. Unfortunately, Freyja is a stick chewer and will also bring hers in the house --- which they promptly go in the garbage the minute her back is turned.
I learned on the farm that small sticks can indeed become lodged in the roof of a dog's mouth. I saw my dad pull more than one stick from the roof of the mouth of one dog until he got older.
Annnnd, FWIW, I had a young horse (around three years) who managed to do the same thing -- aske me how much fun it was pulling a wedged stick from the roof of the mouth of a horse. I've had my own horses for sixty years and that was the only time I ever saw a horse do that.
Meaning, it doesn't matter dog breed or species ---- there are some who just can't keep anything out of their mouths, lollol
Freyja is the most aggressive chewer I've ever had --- you may want to buy some super heavy duty chew toys for Kevin as he sounds as if he is going to be an active chewer.
I buy most of Freya's toys from Chewy.com. They are much cheaper for the same toys than Pet Smart or Pet Sense, which are the only stores available to me that sell toys for hard core chewers. Even our feed stores don't stock safe chews for big dogs --- I guess they think all the XL and XXL dogs in our county have jobs guarding livestock and don't need chew toys, lol