Disclaimer: All names contained in this post have been deliberately made public by the person themself.
Model makers, riggers, musicians, artists, and all others involved in the making of vtuber shows are all carefully credited, since it would obviously be reprehensible not to do so, but the actual performer that portrays the Idol goes entirely uncredited. The performers are all experienced entertainment industry professionals, Hololive does not and has never contracted unproven talent. Most of them have IMDB pages but universally their biggest and most prestigious work is not listed there, because Hololive forbids it.
When Rebecca Cardenas went independent as Dooby one of the very first things she did was make her identity public specifically to take credit for some previous work she’s done. But even after going independent she is still seemingly contractually prohibited from taking credit for portraying Ame, something that might actually be illegal in my opinion. Rebecca should be able to list her time portraying Amelia Watson as part of her professional work experience.
I am not saying that all the talent should be forced to make their identities public, rather I think they should be credited by a name which they control. For example, the performer portraying Takanashi Kiara does not own that name and could not use that name when doing other work, but she does own the name Keekihime. So while some talent, like Karen Calanni playing Mori Calliope, would want to be credited by their real name, others, like Keekihime, might rather be credited by a stage name. The important part being that they control the name themselves and can use it as they wish.
Hololive refusing to credit the performers unfairly shackles them to the company and inhibits their professional careers, and that’s messed up
So yeah, I apparently misunderstood that part of your OP as I thought you meant they weren’t able to talk about their Holo achievements outside the company rather than having to keep their identity separate from the avatar.
As far as I’m aware Cover doesn’t have much problems with the former though I don’t think anyone tried to use it as a springboard for something new. It’s hard to say whether talents not talking about their affiliation with Holo is a contractual obligation or their own choice. Remember that talking about streamer’s alternative identities (let alone real ones) has been pretty much a taboo among VTubers in general. While discussion about PLs shifted with the whole Niji fiasco, that doesn’t mean everyone (including talents) is interested in going full throttle in the other direction.
Talents sharing some things about their personal life on stream doesn’t mean they want everything they do online be connected (whether between identities or real and online lives). Unless one of them says, outright or otherwise, they’re prohibited from taking their deserved credit I don’t see a reason to fight in their name against something that may or may not be a problem. I realize I’m looking at this from a biased perspective as I’m someone very focused on privacy (to the point of trying to compartmentalize my online presence as much as possible) but VTuber culture is what it is and it’s up to those directly involved in it to decide how they want to proceed.
I also think the latter (keeping personal stuff from Holo activities) is fine due to (already mentioned) safety, wanting the brand (avatar) stand on their own and being a way to avoid potential controversies (even if someone finds “dirt” on a specific talent Cover can just go “it has nothing to do with us”). The last one was already used by Cover when some folks tried to stir shit about some of the talents being in relationship IIRC. It might feel strict but it does have its benefits.
Lastly, I disagree that “dropping hints” is good enough reason to spread her name publicly - if she doesn’t say it on stream it’s only fair to keep it to yourself. You said it’s about talent’s choice then post personal info she deliberately chose to omit, why?
I know in Calli/Dice’s case she’s gone on record previously saying she doesn’t care if people see her face / know who she is. Despite that, she still doesn’t go around mentioning the link explicitly under either alias (as far as I’m aware, at least), and still wanted to keep the two separated even when talking as Dice. Whether that’s just for the sake of the stream not being disrupted, just for the viewer’s sake (kayfabe / compartmentalization), or a weak anti-harassment / anti-“anti” thing, or something else entirely I don’t know.
Given how blasé Ame/Dooby (not just calling her Ame will take some getting used to lol) was about dropping the info about her past professional experience etc, it may be that she doesn’t really care if people know but still wants to keep some element of separation nonetheless like Calli/Dice seems to. And if that’s the case it seems like it’s okay to mention it selectively if it’s relevant - it would be difficult to discuss this topic fully without being able to refer to each talent’s other work outside of holo.