Everything we've read so far has indicated that Dragona is willing to deal with Jodio's level of half-understanding acceptance rather than trying to have that conversation with him and risk rejection. Not that Jodio would do that, but that's my guess at what's going on here. Araki is leaving some things as subtext or unspoken for now.
Personally, I don't have the more direct knowledge that comes with being able to read JP and the raw scans, but from what I've seen at least from the way the story was presented thus far, there's a lot more wiggle room in how Dragona's gender can be interpreted.
It could be where they're a trans woman and Jodio simply doesn't know the extent of how his sibling feels about their gender and body, where he honestly does believe it's all about his "brother" being "feminine". Like it was all "oh I just think these clothes would look cute on me", "oh I just like it for the aesthetic" as teenagers and they haven't had any kind of larger conversation about ~gender~ yet. So they'll need to have an extensive talk with him about it later. (I'm leaning towards this personally, but it's quite a bit too soon to call, I'm guessing.)
Or even like you imply, that Jodio hasn't accepted that part of them yet, and misgenders them not out of malice or anything but because he struggles with the concept of his brother becoming his sister, and their extensive talk will be skewed in a slightly different direction than in the prior example.
OR, as signaled by Dragona not correcting anyone's pronoun usage, they might simply not want to apply any labels and prefer to live the way they are where they have physical traits of both sexes and are ok with any perceived gender and pronoun.
OR Dragona themself will go through an arc about exploring their gender because it'll turn out that they haven't decided yet if they see themself as a woman, a feminine man, or someone in between in some way. That they haven't corrected anyone because they simply don't know what they prefer or what feels right.
I honestly could anticipate any of these becoming the plot concerning them, assuming Dragona doesn't die for Jodio's growth or something dated like that.
OR maybe it's all like Jodio says, and Dragona is effectively a crossdressing man - just one that passes really well and for some reason went as far as to get breasts. Not an option that I'm a fan of, but it's one that's still technically there.
So yeah, that's how discourse around them has been going because of no direct first-person confirmation so far of how they see themself: it all feels up in the air, and no one knows what pronoun to use!
I can tell it's very much deliberate because this is effectively just the start of a long-form story setting the groundwork for the characters and we're just getting around to some rising action, but yeah discourse until this is tackled later will be fuuuuuunnnnnn..........
