Cast Through Time doesn't work properly on split cards

[Susucre]

[[Cast Through Time]] gives Rebound to split card on the stack, however the replacement effect does not seem to apply on the card movement.

[github-actions]

Cast Through Time - (Gatherer) (Scryfall) (EDHREC)

{4}{U}{U}{U}
Enchantment
Instant and sorcery spells you control have rebound. (Exile the spell as it resolves if you cast it from your hand. At the beginning of your next upkeep, you may cast that card from exile without paying its mana cost.)

[Susucre]

unit test ignored in 36d6547