In Kurt Vonnegut's book, Slaughter House 5, Billy Pilgrim is captured by the Tralfamadorians, an alien race who live in four dimensions. They perceive all of their lives simultaneously. People, to them, look like '...great millipedes, with baby's legs at one end and old people's legs at the other.'
The Tralfamadorians can move backwards and forwards in their lives - living the good bits and skipping the bad. They have a single eye, in the middle of their palms. When life is unpleasant, they close their hands tight, and wait for it to get better.
The Tralfamadorians teach Billy how to travel in time. They have a lesson for Spider-Man fans also. How do Spider-Man fans who have been reading for twenty or thirty years cope with events like Byrne's Chapter One? Answer: They close their wallets tight, and reach for their back issues.
Continuity is what you perceive it to be. This is fantasy - so believe what you want to believe. Personally, Chapter One is curious, but irrelevant. I have a reprint of Amazing Fantasy #15 which tells me a different story. It's been the truth for over thirty years. Byrne has talent - but am I going to take his word over Lee and Ditko? Like heck!