It's not that it's an unresolvable hole, it's the problem with pantsing in general, what made/makes aSoIaF so good is it's believability, shit happens naturally, shit happens cause of previous shit that happened, no one has plot armor, the story goes where it goes, it's not lead, it evolves naturally. This is great but it suffers at the end of the story, the need to tie things up is inherently unnatural, it's forced, it feels forced 99% of the time cause it is, there's no true end point for a story that's built around shit happening organically, wherever you chose to call the ending, there's still more after that point, unless you force a bunch of shit to come to a head at once. It can be done, but god is it hard to make it feel natural. GRRM can't do it, his parts have too much distance between them, he gave the outline to the show runners and we all saw what they did with it, the last few seasons were a mess of plot holes, teleporting characters and contrived bullshit all to force the finale and it felt distinctly crap because it wasn't what the first 3 or 4 seasons felt like. Plotters have their own problems but given most stories lean towards plotters over pantsers, i don't really think there's a need to elaborate on that, we all know good and bad plotted stories.