Why would it even matter? Like, it's vtubing. All you require is your voice, all else is behind the model. No-one knows your ethnicity.
It's like literally the old "there are no girls on the internet" pasta. The only reason for someone to admit they're a woman unprompted is basically a tacit admission that they're not interesting enough themselves to get by in conversation without that social buff. As a vtuber no-one knows you're black unless you tell them.