oh I get it now Naruto isn't like sans he thinks he looking at different timelines while in reality it is different fanfics people have written and it is viewed to him as other realities I like this idea so much that every fanfic is actually another reality coming to existence
Author's response
You hit the nail on that part. Geno-Naruto does think the fanfics are other timelines and realities; and with all fanfics, they are based off of the 'originator' the Naruto manga.
That is why the timelines are 'finite' and not 'infinite'; and why some are complete and others are not. And Geno can also insert himself in other timelines as well if he wanted. But he doesn't do so because it doesn't interest him anymore.
Until, a different version of himself appeared. Now his interest in the timelines is reignited.