I would say you can call it #ownvoices if you share a marginalized identity with one of the main characters in your book, but the book doesn't have to be about being gay, etc.
Of course, you don't have to if you don't feel comfortable with it.
By default, that's going to be harder for secondary world. Or at least, the link will look more tenuous/less obvious.
I get what you're saying Liz, but intentionally or not it does *feel* like the ownvoices thing is going to be slightly self-selecting in favour of super-diverse diversity (which is definitely an official term). Like when the black-Jewish guy joins the team in Archer and everyone is super excited because he ticks as many boxes as possible, which of course was totally absurd and defeating the intention of such laws/measures. Which then leads to the "not asian enough" thing with that writer as mentioned above.