As a kid I remember that my imagination was way more strong and vivid. When pretend playing e.g. being a pilot of a plane with my cousin , it felt good as if we were doing it in real. Of course we didn't know what the real thing was like. But it did evoke strong visual fantasy feelings.

I got the same feelings reading books with lots of colorful cartoons and things. I use to have a book with characters doing something with icecream so tall it's coming from helicopter or something. They all used to feel SOLID and REAL. Then I grew up and found that book again after many years. I couldn't see those characters and things as real objects anymore.

I haven't read this pdf but I believe other kids do it for the same. Imagination is strong and they could do and be anything pretending.