I would say, however, that a writer should be absolutely confident in their hints they spread out throughout the writing and world, or else they may fall in to the trap of overexplaining or ending up changing the reveal at the last moment because they second guessed themselves in their writing.
I think that your last few words explain everything. It's more than probable that if authors tend to explain too much, or not at all, it's simply because they don't know themselves where their story goes. How can they plan a scene, make the character react by anticipation according to it, when themselves don't know yet that the said scene will exist ?
Just here there's a lot of people who started a thread with, "I have an idea for a game". But an idea isn't enough. You can't start your game just with this, you need to develop your idea, to have at least the main milestones and know how it will end.
Obviously, many professional writers will confess that they were themselves surprised by what their character did. But it was an action/reaction inside the main story. They haven't been surprised because they didn't knew what they wrote. No, they have been because, will writing this part, it suddenly appeared evident that, according to the character personality and the future main events, their character shouldn't react otherwise.
To keep as example my surprise threesome as birthday gift, the author could have planned it to be a deep secret. But while writing it, he suddenly discover that the personality of the girl don't do fine with a so big secret. She's overwhelmed by the anticipation. Knowing how much it will please the man she love is too much for her. The author haven't planed it at first, but to stay put to her personality, he have no choice, she'll phone the MC and tell him everything.
It would be even more of a literary suicide if they looked at the feedback from their players and change the reveal at the last moment just because a few players were guessing at what would the big reveal be.
You know, I'm pretty sure that for too many of the games we have actually, it wouldn't change anything at all.
Take a game like
Lancaster Boarding House by example. It was one of the deepest deception I ever had with an adult game. The story isn't bad, Daniels K is a good writer, and there's quality in the CG. But there's an unsolved mystery inside this game. A secret book lead students to practice a ritual, while other are "part of the secret society". It's nothing dark or deep, it can effectively by seen as just a prank. But they are payed to do this. It's also said that it already existed when they goes in the boarding house for the first time, and that a girl once disappeared after the ritual. And that's all... Only in one of the many ending we have what can eventually looks like an answer ; there's a thought of the MC which is more or less, "I'm sure it's her". I can deal with all this being just a prank, but not with the "I'm sure it's her" as sole explanation, and yet, only in one of the ending.
There's also the teacher. If you play it well, she became your bitch and she let you fuck her while her husband look at the TV not far away... And once again that's all. It's the last scene with her, the last time she appear. You made her crave for you dick... but she never tried to have it again.
And the worse, at least from my point of view, is that most of the players don't complain. It's half a story for the mystery, half a character's arch for the teacher but, no, apparently it's totally normal to end your game on this.
Therefore, would a total change on the reveal be effectively a problem ? Between the games unplanned where the author himself don't know what will be the reveal, and the players that don't even notice when there's no reveal, it would probably works fine. Alas because I agree with you, it should be nothing less than a literary suicide.