Thats where GRRM got addicted to sniffing his own farts about "subverting expectations". Obviously the whole series was leading to an epic showdown between Jon Snow and the Night King, so GRRM had to do something different and subversive.
It really would have fixed a lot to just go ahead and do the expected thing here.
Quoting you but this applies to all of the posts in the last page or so.
The Night King is a show only creation, D&D made him up, he doesn't exist in the books.
So no, GRRM wasn't originally planning on doing shit with Jon Snow vs the Night King or any other such malarkey.
They began deviating from the books from the 2nd scene of the pilot episode 1 season 1 and each season it got further and further disconnected from the books. There's hardly any parallels to be drawn. The last thing GRRM told them that they used was how Hodor got his name, which was like late season 6 or season 7? i dont remember. Everything they were told about how the books were going to handle situation X had to be filtered through the TV plot and it was just a tangled mess since nobody is where they are supposed to be, doing what they are supposed to do, half the characters are dead on the show but alive and play pivotal roles in the books (or vice versa)
The original plot outline (which may have changed) revealed the overall structure:
Book 1: War of the roses between the Starks and Lannisters (ie Yorks and Lancasters from british history)
Book 2: While everyone is fighting over what becomes the war of the 5 kings and distracted, a new threat from the east, the last of the dragon lords, descends upon westeros
Book 3: While everyone was distracted by the Invasion of the dragon queen, the real threat, the real enemy this entire time, the army of the dead, descends from the north to end all life.
So originally yeah, Daenerys Targaryan was supposed to sack kings landing before the battle of winterfell with the undead, but we know that changed by book 3 (book 1 became 3 books long by this point) and Danaerys' dragon dream (prophecy like greenseeing, always comes true but not always correctly interpreted) Is that Daenerys will destroy the Other's at a massive battle at the Trident, so we know that the wights and white walkers overrun all of the north and descend down into the riverlands before they are destroyed by dragon fire.