The info you provided is pretty neat, but this clip does not confirm that hololive gives a base salary. In it she talked about how cover takes a protection fee and how Susan takes a cut, so her salary referred to the money she earned from YouTube ,not a salary given by cover.
Just think about it logically the stream where she talked about it was on the first of April 2020. She claimed that she had just gotten her "first salary"- "FIRST salary". She debuted on the 28 December 2019 . So if cover provided a base salary, why did they not pay her for 2 months? It could be that they are just an evil black company, but if they are why would they provide a base salary at all? Ockham suggest that they simply do not give one.