Depending on the leave plan, companies will have policies where leave should not accrue for a certain amount of time. There should be a parameter on the plan to set this probationary period (ex: 14 days, 6 months, etc).
Leave plans are usually assigned at the time of hire, so this parameter would help reduce amount of adjustments needed on employee plans. Currently, even if an employee has a probation date specified on their worker, there will still be accruals for that time.