Earlier quoted context omitted.
That description seems more appropriate for, say, Roald Dahl than it does for Pratchett. Pratchett was, for the most part, a comedy fantasy author. Most of his writing was appropriate for younger audiences (with exceptions, like Monstrous Regiment), but I wouldn’t call it children’s books. The fact that his Tiffany Aching books are specifically aimed at the Young Adult market suggests that he agreed.
Interesting comparison. Roald Dahl has in his oeuvre many stories that are far less intended for children than anything I have ever read by Pratchett. Pratchett keeps pretty much all of his stories accessable by at least teenagers. You cannot say the same for Dahl.
Dahl definitely has decidedly non-children appropriate work. Fancy some roast leg of lamb for dinner?