"The strings on a kabuto, known as a Kabuto-no-O were never really tied with cords running under the bottom lip as often shown in movies and TV. This was done only when wearing men-gu, (being protective masks such as Me-no-Shita-Ho, covering the face from below the eyes, and Hanbo, being cheek and chin protectors) to hold them in place. The Kabuto no-O were only tied under the chin when wearing nodowa throat protectors. This incorrect procedure has been influenced by Kabuki and woodblock prints, later TV, in which the actors face is to be shown." Credits from Samurai History & Culture Japan
Wearing the knot on the chin historically is wrong, in the last samurai they did it well, this method of tying up the knot on the chin it was used to secure the menpo, this wrong method without the menpo it became popular in kabuki and tv series