So I noticed on my latest boogeyman mask that it had latex that partially covered the neck slit in the back thus not allowing it to fully open near the top hole. I’ve noticed this on many tots masks. Excess latex from adhering the hair I presume. This could definitely create the illusion of some masks fitting tighter than others of the same make. Just an observation 
Yeah that’s happened on my H5 copies I recently picked up, so it does factor in. But it is not the case with my H40 masks, I assure you. One is definitely a different fit than the other. I have absolutely no reason to BS anyone about that, and it just seems extremely absurd to me if someone felt the need to BS about that.
Something is different, only by the slightest margin, but something is definitely different between the two copies I have of the H40. The pre-order copy and the copy I just picked up before Halloween this year, flat out fit differently. Both are the same thickness, both have the same length of cut up the back.
But my H5 masks did have the cuts glued together near the top of the cut, just due to how the hair was laid. So that is definitely a factor in any case or situation when one may come across it.