There are no legal provisions concerning this provision, so it depends on the company rules/policy in this regard. If there is a provision that the benefit is admissible only to the confirmed employee, then it has to be so.
Being made a part of CTC does not mean it has to accrue, CTC is a misleading concept, the effort on the part of the company is to project it by including as many items as possible, including future entitlements like gratuity or other entitlements coming after spending a definite period of service. Employees may not be getting in hand many such benefits, for instance, the insurance premium paid by company will be a part of CTC but the employee is actually not paid the amount.