Spinning Darkness alternative cost is free-cards not exiled

Describe the Bug:
Spinning Darkness if cast with alternative cost doesn't pay the alternative cost ( doesn't exile the top three black cards from your graveyard ).
Which card did behave improperly?
Spinning Darkness
Which update are you using? (date, name)Which type? (duel, gauntlet, sealed deck)
Manalink dev 778ccb5 version - duel
What exactly should be the correct behavior/interaction?
Spinning Darkness : You may exile the top three black cards of your graveyard rather than pay this spell's mana cost.
Are any other cards possibly affected by this bug?
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Spinning Darkness if cast with alternative cost doesn't pay the alternative cost ( doesn't exile the top three black cards from your graveyard ).
Which card did behave improperly?
Spinning Darkness
Which update are you using? (date, name)Which type? (duel, gauntlet, sealed deck)
Manalink dev 778ccb5 version - duel
What exactly should be the correct behavior/interaction?
Spinning Darkness : You may exile the top three black cards of your graveyard rather than pay this spell's mana cost.
Are any other cards possibly affected by this bug?
-