I've seen the Wendy theory and I've seen the counter argument. While compelling, I think the Wendy theory is more of a thing where fans are just looking too deeply (like Room 237) into what is ultimately small continuity things. I think it's less that Kubrick overlooked details, and more, just didn't care. He was more focused on the larger story. Genius can still be genius without turning it into a game of three dimensional chess.

I'm oversimplifying for the sake of brevity, and mean no disrespect to super fans that love to slice/and dice those details, but if the question is about director vision/intention, Occam's razor would tell us that it's just not that complicated.

Edit: also, if it takes 40 years to unearth the real meaning of a movie, it may not be that good, lol. I think it's more simple, and definitely that good.