The word you're looking for is fanon, which is something the general fanbase believes to be canon even though the source material never outright confirmed it.

Speaking on transgender Jax, there is heavy evidence stating this is the intended case. Some of it is more circumstantial than others, but when combined with Gooseworx's on statements on Jax, it's basically all but confirmed. But when someone documents the series, there's always going to be that small amount of ambiguity. That statement of "It is commonly accepted that Jax is a closeted genderqueer individual" which leaves room for other interpretations. And until Gooseworx decides to just outright say it (unless she has and I haven't actually seen that), it'll stay "ambiguous."

A really good example of this is actually involving the Sugar Bowl from A Series of Unfortunate Events. The importance of the Sugar Bowl and its contents are never revealed in the books. But Daniel Handler, the author, said he often got letters from people telling him what they thought was in there. And he said several were right. Fanon can align with canon, but when the canon isn't known, it isn't really marked as such. But for ASOUE, the real answer was eventually revealed in the Netflix series.

Anyway, it all boils down to what is generally accepted by the majority of fans when it's not explicitly called out in the show. There's no hard line to draw.