It's a leftover from hairing the foreheads. Long long ago, when I had long hair and had it cut, I kept the ponytail exactly for such a purpose. It was kinda fun with the headpiece today because I added not only eyebrows but extra trim hair that is pretty much an exact match to my own (because it is!). And braiding your hair is a lot easier when it's in front of you.
I want to try pouring a forehead appliance out of silicone. After the show, certainly. But I learned some interesting things with the hairing, and painting of silicone is a LOT different than latex.