I'm sure it's because it's Father Satan wish for us to be united as per : Al Jilwah: Chapter IV "It is my desire that all my followers unite in a bond of unity, lest those who are without prevail against them." - Satan
The Yazidis have done very well to preserve some of the ancient teachings through the centuries of persecution. This text is not only specifically meant for the Yazidis, but all those who are devoted and follow Satan in some way or another.
Any other groups, individuals, outsiders, who truly consider themselves disciples of Satan and his teaching acknowledge the Yazidi text as a legitimate teaching and reference, whether they acknowledge his existence or not. But it's true that it's of his will that we all have a common and goal to become a collective force to overwhelm and resist the enemy.
This is why I consider some from Cos, ToS and maybe some others like Setians as valuable allies when it comes to the common idea that Xianity and the Judaic religions should be opposed. We each serve a similar interest and have learned from each other.
Though I'll always consider JoS to be the closest intended path of Satan which is the clearest and most straightforward, and the closest one can achieve and experience a small form of "elitehood". I believe that if other organizations adopt or even acknowledge a portion of its teachings that's still a win, gradually they will accept this is the true intended path of Satan.