I'm not sure but I think with some of the longer haired breeds like Yorkies, ShihTzu, Tibetan Terriers etc the hair is naturally parted along the back, but I don't know if it extends to the neck area. And of course, RR's have that funky ridge of hair, but again, not on the neck. In all likelihood, I'd probably just consider your guy's unusual hair growth to be a cowlick. I've seen that often times along the bridge of the nose.

As for applying flea control etc there, I always apply it a little further down the back so it's not actually on the neck, more 'between the shoulder blades' as recommended. That's probably the optimal spot so the dog can't either lick it (if further down the back) or scratch at it (if on the neck area).

 

I've tried to apply it further down, and he can lick it.