"They come to realize that their bag fell."
Translation:Mereka menyadari kalau tas mereka jatuh.
They come to realize that their bag fell.
Meaning: Mereka menyadari kalau tas mereka jatuh.
Mereka menyadari bahwa tas mereka jatuh.= not accepted, reported
I think 'kalau' cannot be used here to translate this English sentence.
'kalau' = when/if
It would give the sentence a different meaning.
Is there any reason not to just say "They realised that their bag fell?"
EDIT: Now that I've noticed the "Kalau", I'm wondering if it's more "They would realise if their bag fell"
Yes, this is the only time that we have to translate "kalau" as "that". It's inconsistent, and quite frustrating and unfair to the learner (I get it wrong every time!)