If you think they're sub-optimizing because of biases and a poor process, maybe that represents an opportunity for you or someone else to use your method to outcompete them.
Their track record suggests they're doing pretty well.
So your argument is that they should be above examination of their interview process because their investments are doing well? Come on, you're just arguing for the sake of it now.
Multiple independent assessments are great at reducing random noise. Bias is noise, sure, but it's by definition not random so you need other forms of intervention to counter it.
Their track record suggests they're doing pretty well.