Yes, if its a calendar year plan.
Isnt this simply saying that you apply the definition of 5% owner in Section 416 to the period defined in 401(a)(9)? It doesn't say anything about a determination date (which is also in Section 416, but in a different section from the 5% owner definition). Instead, apply the 5% owner definition (416(i)(1)(B)(i)) to the period defined in 401(a)(9) (the plan year ending in the calendar year in which the employee attains the applicable age.)
5-percent owner - 416(i)(1)(B)(i)
For purposes of this paragraph, the term "5-percent owner" means-
(I) if the employer is a corporation, any person who owns (or is considered as owning within the meaning of section 318) more than 5 percent of the outstanding stock of the corporation or stock possessing more than 5 percent of the total combined voting power of all stock of the corporation, or
(II) if the employer is not a corporation, any person who owns more than 5 percent of the capital or profits interest in the employer.
Determination date - 416(g)(4)(C)
The term "determination date" means, with respect to any plan year-
(i) the last day of the preceding plan year, or
(ii) in the case of the first plan year of any plan, the last day of such plan year.