The collar sleeve position is a great starting point for setting up your attacks from your open guard. Super effective for setting up the omaplata and triangle as well as some of the newer movements such as the berimbolo, farside collar sleeve, and matrix style attacks.
Developing a guard game no gi is not easy. Especially for athletes crossing over from gi jiu jitsu with the abundance of grips. Since we are limited in our grips in no gi we have to make full use of both our upper and lower body. This might also explain the usage and acceptance of lower body attacks in no gi.
The darce choke is one of the most popular and high percentage chokes from side mount especially when your opponent turns into you to recompose their guard. Definitely a move that will be used a lot this year.