If that is said anywhere, it's not been universal in application.

Over many years, including earlier this year, I've seen US passports sent in with renewal applications where the passports had years and years left on them before the expiration date. And the applicants were issued new passports. One such application where the renewal was issued for an applicant whose submitted passport wasn't expiring for several years literally had it done this year because the bearer didn't like the printed date of issue on the passport as it was a reminder of a bad day. And I have a lot of other examples of renewal passports being issued for people whose submitted passports weren't expiring for years and years and yet had other reasons -- from the trivial to the very material -- to renew years in advance of the printed expiration date.