Read the statement about her graduation again, anons.
https://cover-corp.com/news/detail/20220712b/>We had discussed several times with Tsukumo Sana regarding the direction of her activities, however, as time went on, it became difficult for her to continue her VTuber activities. The key phrase here is "several times". Cover had a long term issue with Sana's content that they tried to get her to correct and she didn't. Obviously, this is her stream output. Cover talents are supposed to be able to produce 3 hours of live stream content minimum for a period of at least 1 year, barring some circumstance that prevents it for a length of time. This "one year" line is why Holos like Ayame, Aqua or Gura can dial back on streams after that point. Check the application page for becoming a Holo, it lays it out clearly.
>After much deliberation between both parties, with the deepest regrets, we have decided to honor her request for graduation.Sana and Cover chatted it out, and she decided to graduate as she didn't want to ramp up her stream output.