The IRS description of the exception you are asking about is "the employee separates from service during or after the year the employee reaches age 55 (age 50 for public safety employees of a state, or political subdivision of a state, in a governmental defined benefit plan)"
The exception applies to distributions from the plan provided by the company from which the employee separated from service during or after the year in which the employee reached age 55. If the employee separates from service from this company before the year in which they reached (or will reach) age 55, the exception does not apply.
