What is the difference between Encounter.indication vs Encounter.hospitalization.admittingDiagnosis?

The definition of Encounter.indication includes "For admissions, this is the admission diagnosis."

The definition of Encounter.hospitalization.admittingDiagnosis is "The admitting diagnosis field is used to record the diagnosis codes as reported by admitting practitioner. This could be different or in addition to the conditions reported as reason-condition(s) for the encounter" When/why would the hospitalization admitting diagnosis be different than the Encounter.indication (a.k.a. admission diagnosis)?