The Reivers, aka the Insane Clown Company or Gigolo Marines, are the new units meant to act as a
way to phase out proper scouts assassins. They are meant to go in before the initial assault and harass the enemy using fear and terror… not unlike the Night Lords. They spread fear (or humor) with their specialized skull helmets which look absolutely ridiculous. The skull itself looks more cartoonish than menacing, guess Guiliman was hoping the enemy would laugh themselves to death, and I had no idea that the top part of the helm - you know the most important part - was detachable. But hey, maybe GW did not know how to put skull designs on helmets, maybe they never used them before.
There is no connection! You’ll be wrong and labeled as a heretic if you believe there is.