He’s said he doesn’t care about people being spoiled period because ‘it’s the journey that matters’ so that’s probably his mindset.

Regardless I have read a number of comments online from people who have been spoiled (including this thread) so it’s something that has been brought up. Even the Nocturnal Readers newsletter put out a message about it warning newcomers to be careful.

I'll also add that at this point King has been writing books longer than a number of his fans have even been alive and they would probably consider themselves 'constant readers' but still have yet to read all his work or are not reading his work in chronological order.