The grades are explained at the bottom of the page.

Regarding Startpage, It's not mandatory to show the cookie banner if you don't track. Startpage doesn't track you at all, so it's grade A.

Wikipedia has that all the bad things happen to your account except for the tracking, but you can still use Wikipedia without using an account. I agree that it's a B.

I'm not familiar enough with Tor to answer that grade.