I guess I kind of understand why people call trans/nonbinary/queer Steven Nora but if we're coming at this from a strictly canon sense- that as far as we know, Steven was born as Steven and isn't transmasc (in a literal, 100% canon sense, anyway)- I don't really think that the same Steven that we see constantly struggle with self identity, especially including the episode the name Nora is introduced, would "choose" a name from Rose Quartz/Pink Diamond, especially if it was before Rose shattering Pink was dropped.
Like if you struggled your whole life with being called the wrong name and pronouns you don't use, and living up to a legacy that you don't fit into, and, post CYM, convincing an entire society of beings who had lived thousands of years that your mom that you're given the same title as isn't the same person as you, and then you'd pick the name that your mom would've given you anyway?
I understand the concept of the name Nora as a gift from Rose and why it'd be significant to take that name on, especially since canonically Steven Quartz Cutiepie DeMayo Diamond Universe is a name, (although one could note that all of these are names given from someone else) but if post CYM timeline is at all in play I really doubt that the name that Steven decided to change it to forever (weird semi immortal shit) would be from Rose.
In reality I know people probably just call them Nora Universe as a catchall tag for people looking for #Girl Steven which is understandable but I just cannot picture her ever wanting to take that name willingly...
I think that's one thing that makes a transfem Steven so compelling narratively to me, because canonically only the name the Diamonds use matters to Steven, there's never really a moment where mistaken identity is associated with "but stevens a boy!!11!!" textually, which is much appreciated for many reasons. Femininity and gender non conformingnessism has always been something positive in Steven's life, through gem fusion (literally becoming another person, another flavor of gender) or with humans, like the fit from Sadie's Song and the lack of bigotry Steven faces for being "kind of gay bro" by having actual emotions and wearing pink and shit.
But at the same time, can you imagine the absolute nightmare that would be to make that decision to come out? If your entire life, you had to justify that you are yourself endlessly, and suddenly, something that you thought of as immutable- your own name and identity as Steven- is something that doesn't fit you anymore?
It's a narrative that isn't quite related to gender dysphoria, but more so as a conflict with identity as a whole; how do you convince yourself to do something that, in the minds of you and everyone else, brings you closer to being your mom who you think sucks and who you want to separate yourself from to the point of having numerous PTSD episodes by the thought of it?
Ultimately though Steven is trash at naming things (Lion, Watermelon Steven, Cactus Steven, Cat Steven, MC Bear Bear if that wasn't already its name, Tiger Millionaire a rich tiger and Purple Puma a purple big wildcat, the Slinker, Centipeedle...) so this is one of the rare cases for trans headcanons where I almost feel like her name being Stephanie or something derivative of Steven would make sense, because like...yeah I can see her doing that and thinking its the best name ever lol.
If I had to come up with a canon name though it'd probably be Star because every single other AU creator on earth has come to that conclusion and it fits so well narratively it's kind of unbelievable. This is all in the realm of theorycrafting though, so, for all we know her name would be like, Steven 2 or something, which, good for her no matter what