You must not be up to speed on the level of special effects makeup and mask artistry in Hollywood.

It may not be absolute proof or evidence in this particular scenario. But to suggest that masks aren't that realistic is far from an informed opinion.

P.S., the darkness under the mask is not indicative of the color of the person's skin. When you're under studio lighting - or any lighting for that matter - it's very easy to create a shadow. A sloppy job by the special effects makeup team, not attaching it fully to the rest of the neck, could just as easily create this shadow and movement.

But believe whatever it is you feel comfortable believing.