Answer :
Well, if the boy is anonymous and is not known throughout the book than
that allows the reader to experience a sense of making up the character
in the readers image. Usually this kinda puts you as the boy if that
makes sense. When the character is known than it gives the reader a
different experience with imaging this character from a 3rd person
perspective. The theme of it would basically just be that if or if you
don't mention the main character determines if you imagine the
characteristics of the character or not.
Hope this helps! XD :)
Hope this helps! XD :)