Wish I had something constructive to contribute, but all I can say is that ATG is a no-no for me anywhere, and I'm also in the majority of having bizarre neck growth patterns.

I actually go ATG on individual whiskers near my Adam's apple (literally less than 10 hairs) and the rest of my neck is done with either diagonal downward strokes from chin to shoulder, or XTG strokes from Adam's apple towards ear. I have to angle the blade if I do an explicit sideways stroke so that the tip isn't threatening my neck.

You're right in that it's probably technique in that specific area; not that you have bad shaving technique per se, but probably that figuring out the neck's growth pattern is one of the more difficult aspects of wet shaving altogether and something that I'm still experimenting upon almost 2 years in.