And what about the case when you have information in the header record that needs to be associated with the detail records? For example, if we have an employer group in the header record - and the detail records are the list of employees for the group.

I have worked with files where the group identifier only exists in the header record, but we need that identifier for each detail record.

I don't think that can be done with a conditional split - and using a script component will work handily.