It looks like he does. He does also look kinda chubby. If you take your fingers and run over his ribs, can you feel them right off, feel them but faintly, or do you have to press in to feel the ribs?
If you have to press in to feel his ribs, he may need a little diet or more exercise. If you feel them, but faintly, then I would not worry too much about his neck. Some horses are naturally like that.
My Lipizzan mare has a slightly cresty neck, but she isn't fat either. And I had someone tell me, "Watch out she's going to founder!!! She needs to loose weight!"
No she isn't, and no she doesn't. I can feel her ribs, but they are not visible. It's how she's made...
Trust me... she's not fat... I don't like fat horses.