Mephisto in Boss Rush does not consume soul charge for using Lv1 Special-Is it a bug?

Does any notice that Mephisto in Boss Rush event does not need to consume any soul charge for using Lv1 special. There is no such effect on the boss node and the skill description indicate he should consume one soul: "Special 1: Soul Imprisonment – Mephisto blasts lava from his mouth and then immediately summons a mystical wave of bones, imprisoning the opponent’s soul.
Consumes a Persistent Soul Charge to imprison the opponent’s Soul, reducing their chance to activate Buffs by 100% for 15 seconds.
Incinerates the opponent, dealing 688.8 Energy Damage per stack over 4 seconds. This also removes Perfect Block Chance and reduces Block Proficiency by 50%."
Consumes a Persistent Soul Charge to imprison the opponent’s Soul, reducing their chance to activate Buffs by 100% for 15 seconds.
Incinerates the opponent, dealing 688.8 Energy Damage per stack over 4 seconds. This also removes Perfect Block Chance and reduces Block Proficiency by 50%."
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Comments
Is this accurate?
Do you suggest him as a War boss or on other nodes like something that not oblige him to do the sp1 and keep then the souls?