They cement the original attack, declare that the attacker would have made the same “non-apology apology” back then, and thus brings it up-to date — proves that he did not change.
“Non-apology apologies” are conditional — they include an “if.” This means that the speaker feels no remorse, no regret, no wish-they-hadn’t-said-it. And it allows the speaker to walk away, feeling guilt-free because he deludes himself to feel he did nothing objectively wrong. Just some people in over-sensitizing the comment, took it the wrong way.
So he “apologizes” only to them, thus ridding himself of any possible remaining negative feelings about it, while retaining — affirming — the belief itself, and so leaving his (delusional) self-esteem intact.
Just some beginning ruminations on this from a non-psychologist.