The Volcanic Orb attached to the player during Flame Rush, with the Magma Starter skill node enabled, does not unleash the final wave of shrapnel when detonated.
To reproduce:
Specialize in Flame Rush and spend one point in Magma Starter.
Throw a Volcanic Orb and watch how the orb detonates into a larger amount of shrapnel when it ends.
Cast Flash Rush and watch how the larger amount of shrapnel does not fire when Flame Rush detonates the Volcanic Orb attached to the player from Magma Starter.