If the disability benefit does not detract from the deferred compensation it is a disability plan and not a pension. Your example states that as long as the actual pension amount is not diminished by the disability benefits the disability is then an auxiliary benefit. A disability benefit is further defined by its qualification requirements, if a participant is required to be certified as disabled by an outside entity, usually Social Security, the disability plan is disability plan as long as the retirement pension at the Normal Retirement Age is not reduced.