For purposes of paragraphs (3), (5)(D)(i), (8)(D), and (8)(E), the term “retirement age (as defined in section 416( l ) of this title)”, with respect to any individual entitled to monthly insurance benefits under section 402 of this title , means the retirement age (as so defined) which is applicable in the case of old-age insurance benefits, regardless of whether or not the particular benefits to which the individual is entitled (or the only such benefits) are old-age insurance benefits.