An armchair expert with no practical art experience doesn't like his "correction" being critiqued and question, yet is very generous with his own. So you're a painter are you? Perhaps a draftsman? Or just a troll who's bored?
Perhaps you should actually do some art study and training, and then practice, rather than looking up Wikipedia entries.
There are plenty of professional artists with more practical experience than you that make give the same explanation as this artist.
https://www.proko.com/shading-light-and-form-basics/
But, I guess you wont read this either.
Of course I will read it why would you think that I have a problem with reading. and who got you to be devils advocate. I already warned you for my downvote. I have already send an email to the official site and I wait for a reply from the artist until then you get a last warning. I am not having any issues with you.
I do sculptures and paintings as well. I don't think its a big of a deal I ve win awards at Amsterdam for a painting as well. Next time you reply to me dictating shit you get a full downvote last warning.