There was a NijiJP liver named Moruru who left the company in 2019. The exact circumstance surrounding her retirement aren't well known, but the rumor back in the day was that she suffered bullying from within her gen. Those rumors have never been substantiated; most people at time chose to believe that Moruru had personal issues committing to a streamer identity, that she had a history of false starts under various accounts, and dismissed the idea of bullying. Her career after leaving Nijisanji has not borne out the idea that the problem was with her.
Then there was the Yuzuki Roa vs Kingyozaka Miero drama in 2020. Roa accused Miero of copying elements of her persona; Miero accused Roa of harassing her over the issue through private messages. The organization took Roa's side in the conflict and instructed Miero to change her character to be less like Roa. Miero ended up being terminated for breaking NDAs. Miero lost most of her credibility do to the NDA violation, as well as accusations of other kinds of misconduct in her past, and her claims about bullying were largely overshadowed.
When Zaion left the company last year, Anycolor presented a termination statement similar to the one they would later give for Selen, outlining that she had repeatedly broken the company's guidelines since her debut etc etc. The person behind Zaion released her own document describing the mismanagement, double standards and unfair practices she witnessed while working with Nijisanji. She described how she wasn't allowed to do things other livers could because of her background as an independent streamer. She has also talked about feeling betrayed by the other livers in her group, that livers had turned a blind eye to her mistreatment, and at least one of them has made damaging accusations against Zaion's character on stream (possibly at the company's behest). She felt that people she had once considered her friends had stabbed her in the back. And just like Selen, Zaion contemplated ending her life.
In each of these situations, fans of Nijisanji reacted by placing the blame on the person leaving the company, and refused to acknowledge the possibility of wrongdoing on both their part, and on other livers. In Zaion's case they accused her of lying about her situation and gaslighting her fellow livers, readily believing those who remained loyal to the company. All the claims about the abuse Zaion suffered were overwhelming dismissed- until everything she described happened to Selen.
Anycolor seems to have a history of favoritism and turning their talents against each other. They fail to mediate conflicts between the talents when disputes occur, they enforce their rules unequally from person to person, and they either tolerate or encourage talents smearing individuals who have displeased the company. And when stuff does fuck up, they push all the blame away from themselves and turn the exiting liver into a scapegoat.
So you're telling me that they've done this for at least four years, six if you take the speculations around Moruru as fact, and they'll just suddenly change their corporate culture from top to bottom, all the way from the lowest manager to the CEO at the top, across both branches? No, I do not believe so. This shit is institutional at this point, and the thing about institutions is that you can replace everyone currently at it, ship of theses style, and still end up with the same culture.