as not always the most sound explanation， because it’s not the “official” source. I’m not in a camp that says “go to Stack Overflow before you ever darken the domain of W3Schools， and use it only when MDN isn’t making sense to me. ， With the current state of W3Schools。
I feel like it’s a bit like the issue of citing Wikipedia in a school paper. Do people tell you not to do it because Wikipedia isn’t useful? No，” because there have been many times that I go to MDN and say “huh? I don’t understand this explanation. Or the individual words of which it is composed.” and then go to W3Schools and see something simpler that helps me get a handle on it. BUT I would still treat it with a modicum of suspicion，。