[user104658]

Originally Posted by Dezzy

I wouldn't say that that an outline of the plot from before GRRM even put pen to paper is particularly spoiler-ish. You can write out your outline but you'll rarely stick to it since you'll get new ideas and inspirations along the way.

The ending to my first book was planned to be completely different than what it ended up being because once I got to that ending, I was in a different place to where I was when I wrote the rough plan, lots of things ended up different, some characters that were meant to die lived, some that were meant to live ended up dying. I imagine such an outline wouldn't be so readily available if it reflected the ending that GRRM envisions today.

You "get to know" your characters too, they become living beings with real personalities instead of just an idea, I imagine especially if you're writing them for 20+ years, so for example when he wrote that Jon and Arya get together they were just vague ideas and then when they actually were written and fleshed out he might have tried to envision a romance plot and been like "Lol neither of them would be interested!"