This is fascinating. The Shining is one of my favourite films and I've seen it a few times but I'm not going to pretend I've ever understood exactly what happens
All of this makes a lot of sense though. I just googled the thing about Jack reading a Playgirl and apparently that particular issue he was reading featured something about incestual relationships, particularly parents who sleep with their children... it's amazing how meticulous Kubric was in including all these things, such tiny details that you'd never notice unless properly investigating. Even if you spotted that it's a playgirl he was reading you'd never know just from watching the film the relevance of that specific issue.