Rule 608.2d, in turn, states (emphasis mine): 608.2d If an effect of a spell or ability offers any choices other than choices already made as part of casting the spell, activating the ability, or otherwise putting the spell or ability on the stack, the player announces these while applying the effect.Although it might be completely trivial and unnecessary to state, which half of a split card to cast is a choice (made during the casting process)
Take a card like +2 mace
This is going to result in some pretty powerful cards, as this allows Sagas to add to the board immediately in addition to getting the chapter effects
Here are my top picks: Duskmourn House of Horror Commander Deck: Endless Punishment This deck is a dream for anyone who loves horror themes and grindy value plays
How do I securely pack my cards/collection
Last but not least, if you cast Harmonize with an empty hand, you mill 3 and draw 0