I've done a fair amount of reading on it, as I have a LOUD snoring problem. I have never seen any mention of muscular necks making the problem of snoring worse, but body fat does. Body fat inflates the soft palate and uvula, which add to the closing up of the throat. Muscle tissue, if anything, would stiffen the interior of the neck, I would think, and thus help relieve the closing of the throat. Also, sleep apnea and snoring come hand in hand, but are NOT the same problem. I snore, but do not have sleep apnea. The difference is that you can snore all night but never stop breathing (me), or it is also possible to have sleep apnea but barely snore at all. There is a lot of confusion and public unawareness on this. Sleep apnea happens when your soft palate rests down on your throat, and you don't continue to breathe in your sleep. You wake up repeatedly to take a breath, and in bad cases, you might go long enough to hurt yourself between waking up to breathe. So it's serious business.
Just to clarify on my problem: I don't have a very large neck at all, and my body fat is around 5%. So I have a small, lean neck, and still snore.
Charles