I took "systematic bias" to have similar meaning to "systematic error" meaning that there is a constant shift on every data point. Admitting the possibility of bias is very different than admitting bias in every single trending content decision.
Edit: though I see you've used systematic from the start, so maybe that was your intention.
They don't have to admit bias in every content decision. They have to admit systematic bias in content decisions in the aggregate, which does not necessarily imply bias in every content decision.
While it is technically, theoretically possible that their system is open to the introduction of these biases but does not actually exhibit those biases in the aggregate, it is astoundingly unlikely.
We're in agreement there. A company that is progressive-liberal by nature is going to show some of that bias the company's actions. Even with a conscious effort to avoid bias they'll fall prey to biases they aren't aware of.
This seems to be a game of how much complexity and nuance one can add to a simple story. By introducing "bad actors" and "systemic risk", I'm not sure we're helping anybody understand anything better and instead most sixth-grade readers are probably just going to tune out.