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.