You are expecting the "End date" in your SFAPI CompoundEmployee response, but you could not find / it is not being returned as API response.
SuccessFactors Employee Central - SFAPI CompoundEmployee API in Delta Transmission Mode
Reproducing the Issue
Run your SFAPI CE delta query and observe that the XML tag <end_date> is not found in some nodes.
Since period-based delta transmission is designed for consumers that are not able to handle effective-dated entities and future changes, it ignores end dates of time slices that are outside of the given period.
The description of this behavior can be found on the guide section 4.1.1 End Date Handling
SFAPI CompoundEmployee, Compound Employee, end date, end_date, <end_date>, not found, missing, cannot find, not being returned in the response. , KBA , LOD-SF-INT-CE , Compound Employee API , LOD-SF-INT , Integrations , How To