It really is all there is to it.
Playing devil's advocate, but I do get why it matters to some, especially fans of chuubas with smaller audiences. It's not necessarily about wanting to end up with them, as much as feeling that the respect and affection between a fanbase and the chuuba is to a degree, mutual.
A big part of the appeal of watching smaller chuubas (if you're not straight up trying to groom them) is the community and interaction. The idea that some secret boyfriend is seeing all this going on (as a mod or manager) would be genuinely bothersome to a fan, even if that fan knows that there will never be a real relationship between them and the chuuba.
In that respect, I don't necessarily agree with the notion that nothing a chuuba does off-stream matters. It still does. If it turns out that a VTuber was shittalking their fans on a private account and it leaked, it would still be a major yab and it would (rightfully) affect people's enjoyment of that chuuba.