Good collars have two pattern pieces: a top collar and an under collar. The Top collar is bigger than the under collar because it has to go over a higher "hill" (the roll of the collar -- I think it is called "turn of cloth") and also because you want the seam line on the outer edge of the collar to role underneath the collar.
If the collar pieces are the same size, the collar will stick out, almost like an Elizabethan Ruff (think Shakespeare).
But raising the top collar's neckline from the Centre Back round to near the Centre Front by 1/8" (3mm) makes it's neckline a little bit smaller than the neckline on the bodice. Surely this is wrong? But no. If you think about it, the collar will be inside the neckline, so to fit smoothly, it ought to be a tiny bit smaller (just like a telescope's parts). I suppose you could not bother with this adjustment in a very lightweight fabric such as with a voile blouse.
So, I would suppose that with thicker fabrics, like in tailored jackets and coats, and when you have a faux fur collar, the neckline on the garment ought to be bigger by at least the thickness of the fabric.
The "telescope concept" (yes, that'll do for a name) was really baffling me last night, but now I've figured it out it makes perfect sense, and I thought I'd share it with you. I hope it helps you as much as it does me. : )