honestly having read that book the description is so robotic that I do not think it was for wank material. I do think it was a genuine narrative choice he decided to go with to show that they have become more mature since their first encounter with pennywise. Especially since King hasn't done anything remotely similar since I just think it was a byproduct of being on coke for like 15 years lol
that being said its a horrible scene and a horrible idea. I just don't think he's a pedo
as for books better than movies. I wouldn't say better but I do think Knock at the Cabin as a movie is on par with the book. both are very very good in their own ways