Does Google manually adjust weights? While I agree with you, I always supposed that Google weights websites according to their own algorithms, not because some moderator thinks that it's less informative. If w3schools is higher, probably there are technical reasons, for example more users prefer it (may be content is easier to understand).
> The Manual Actions report lists instances where a human reviewer has determined that pages on your site are not compliant with Google's webmaster quality guidelines. Google's algorithms can detect the vast majority of spam and demote it automatically; for the rest, we use human reviewers to manually review pages and flag them if they violate the guidelines. Flagged sites can be demoted or even removed entirely from Google search results.
Specifically mentioned on that page is "Redirecting users away from the image on the site when the user clicks "view image" in Google search results" as an example of "image cloaking behavior".
