There's one piece of evidence that supports it not being retroactive. It's not explicit, just implied. Akura Fury is Malice's son from before she reached Monarch (but probably not much before, because it's mentioned that he failed to bond the Book of Eternal Night that became Mercy's), and he does not have purple eyes and we've never seen him deploy the armor in canon, unless I've missed something.
It's possible that he just never had a reason to use it "on-screen", but I suspect that he doesn't have it as a power. Since Charity is his daughter, you'd think that this applies to her, and I also don't recall her using the armor. Fury had a broad and deep line of descent, and they might all not have the bloodline armor unless they got it from their other parent.