Same reason I don’t trust it - imagine rating fking BBC (the literal pro-state violence, austerity supporting, anti-immigration governmental mouth piece as “left-center”)
It just distorts people’s perception of what political biases are and makes them complacent by relying on an automated bot to do the important work of using your own judgment for what constitutes as moral or justified.
By letting it platform itself on lemmy, it’s basically inserting itself as the de facto expert on the topic - so for example, people overseas might see BBC rated as left-center and highly factual and start believing that wanting to “secure your borders” is a thing that UK leftist want. Well excuse me if I don’t want a privately owned (even if open source) US company deciding what political views others should have.