Isn't it weird that Tom Zane wrote a detailed Page about Alan's Childhood?

At the end of Aw1 when we find the Shoebox and the Page about Alan as a Child that's supposed to be written by Zane, do we even know that it was Zane for sure or does Alan just assume it?
He was a Poet or maybe a Filmmaker at that Point so why would he be writing detailed Paragraphs?

Wouldn't it make way more sense if future Alan was the one putting it there, pretending to be Zane to set himself on the Path or did i forget about other Instances where we see Zane writing like that