Do you have a link where I can read more about this? I'm surprised kids find third-person difficult. My eight-year-olds and their friends are all starting the Harry Potter books, and I haven't heard this complaint.
I've got some young advanced-reader kids (I think my eldest had read all but the last couple Harry Potter books before turning 7? And they did understand them, we quizzed 'em quite a bit to make sure) like that and the difference is we're handing them older books we're familiar with before they'd ordinarily get to them. Most kids track closer to normal graded reading level and will learn largely on newer, first-person books provided by teachers and librarians who are desperate to get kids to read anything.