That was my guess as well, though I'm not sure why management would offer re-branding - as in, I'm not sure what they thought the Noctyx members would gain from it. Like most users here, I'm more familiar with Hololive. HoloJP5, 4, 3, and Council didn't re-brand. (Edit: Council did become CouncilRyS, but that's relatively minor and it started even before Sana's graduation tour.) They may not have been given the option, but I don't see what they would have gained from it. I've heard that idol groups do that, but the only corpo Vtuber group I can see considering re-branding if they lost a member is HoloX, and even then they might refuse.
The Meloco thing goes back to that discussion about whether English-speaking Japanese now prefer to apply for EN spots instead of JP spots. NijiEN, by virtue of having more spots, has more room for ESLs - so long as they're willing and able to adapt.