He also talked about their first interaction on FA and how their relationship started as he helped her (a fan at that time) overcoming the end of a bad relationship and her damaged impression of the furry community (second comment in the journal you linked).
Yes, he admitted dating a Minor, but he also made clear that this did not begin with dating. He didn’t give an exact timeline allowing us to know the tame it took, but this began on FA. A site with very adult contends that is not really suited for minors and no really save method to check the actual age of its useres.
At what time he learned of her age (and how old she was at that moment) is completely up to speculation, but the indicators that she was 15 when it started are from the troll-account on X formerly Twitter dedicated to hating Kabier, a source absolutely not trustworthy. But with the situation given there is a fair chance that he initially assumed her to be an adult.
But is it strange that they became friends and then fall in love?
And again, ONE CASE DOES NOT PROVE A GENERAL POINT. This happening one time makes him not a pedophile, it would if it happened multiple times or started as a sexual thing, but not the way it did happen. (Though we have to take JasonAfex word here, as proof is missing, but at least Kabier did not said it to be false)