Factual error: In the scene where Bobby and Mike go into the comic book store, you can clearly see a Transformers comic on the shelf. But the movie is set in the late 1960's/early 1970's....and Transformers did not come out until the 1980's.
Factual error: The walkie-talkies the kids use at the end of the film would not make the squealing noise they do. The walkie-talkies they have transmit on high enough frequencies that this would not happen. Mediumwave and Shortwave have this effect, not walkie-talkies.
Answer: Deliberate production choice, and to show him from the younger child's point of view - also remember The King, when in his drunken state, is a child abuser, so the younger boy will see him as a large and terrifying presence - that is, so big he won't fit in the frame of the shot.
Neil Jones