Regarding professors wanting to keep review data tightly sealed: in my view, if you can't by public disclosure of your evaluation, then you either don't feel you're meeting expectations, or have no desire to improve in areas where students feel improvement could be made.
Also, the biases pointed out in these reviews aren't unique to academia. Gender and age biases exist everywhere. This article sounds like it's just pushing the idea that students should have less influence in the hiring and promotion decisions of professors. You know, the very people that the teachers first and foremost serve at a university.