Sometimes it's actually unethical not to Spoil a story.

When Doki Doki Literature Club first blew up back in 2017, one aspect of the conversation around it was occasionally how the Tigger Warnings at the beginning kind of Spoils the game, and yet it would still be wrong not to have them.  Fortunately the game is good enough at immersing the player during the hours it spends pretending to be a normal Visual Novel that you may very well have just forgotten about the Warnings by the time stuff starts happening.

DDLC's trigger warnings fortunately did not have to be very specific, there are lot of things they could have been referring to.  And even more Fortunately one potentially Triggering trope DDLC does not do is have a twist where a character we thought was a Cis Woman turns out to be a manipulative psychotic Trans Woman serial killer.  If that had happened, it would in my opinion warrant a more specific trigger warning.

That is a very specifically problematic trope that may be very potentially triggering to some people not necessarily inherently bothered by any broader trigger warnings it could be classified under.  But it is also a trope that is inherently a twist, you can't warn someone that it's coming without Spoiling the story in-question.  But I have no respect for the artistic intentions of creators who choose to use that damaging trope.  I am still a Libertarian when it coms to Free Speech, I have no desire to ban works that engage in Problematic tropes I hate, but the people who want to avoid this Trope also have the right to be warned about it.

In the case of this Trope it goes beyond being unethical to not spoil it, I'd call it outright Immoral to try to prevent people from giving this plot point away on the grounds that preserving Twists is some inherent virtue of your personal Internet Ethics.

I'd been playing by the old rules even though I've felt this way on the inside for awhile.  The Umineko Visual Novel does this trope yet I still didn't discus it till after the Spoiler warning in my Umineko post.  And NezumiVA is a Trans Woman Anituber who did an hour long spoiler free video on Umineko.  Some Trans Anime Fans aren't bothered by what Umineko did, but they need to understand that their being okay with it doesn't mean others will be, and some younger Trans Anime Fans may assume that because someone like NezumiVA recommended it without any qualifiers it must be completely free of any Transphobic tropes only to be very triggered when they invest countless hours into the VNs without any warning of what's coming.

Again I've been guilty of what I'm criticizing here myself in the past, I increasingly feel guilty how often I've recommended Pretty Little Liars to people while forgetting to bring up it's use of this trope in it's last 2 seasons.

That's just one example of an inherently Problematic Twist, there are others I'm sure, but this is the one I have personal experience with.

But after that is the perhaps more trivial but still worth discussing matter of cases where how something is marketed makes an aspect of it a Spoiler that clearly shouldn't be based on how the text itself is written.

Catwoman: Hunted is an animated movie that has no twists, saying exactly how the villain is defeated in the end can still be called a Spoiler, but the identity of the villain certainly is not.  The movie is NOT a mystery, who the main antagonist is is obvious very early in the film, way to early to at all be worth calling a spoiler.  Yet I got in trouble with a prominent YouTube channel on Twitter for referring to that villain on the grounds that it's a Spoiler.

The only reason the identity of the villain can at all be considered a Spoiler is because it was Marketed as if Black Mask were the villain. he's the only antagonist on the Cover.  But in the text itself he obviously is not the main villain, he is set up as less important then Minerva from the start.

I don't know why they did this.  It could be the film entered production before Wonder Woman 84 came out with the expectation that it would make Cheetah a big deal, but then after it had poor reception from the loudest online Nerds they decided to avoid the now tainted character in how they promoted it.  Either way though when something clearly not a twist in the script is inexplicably concealed in the marketing, I feel professional reviewers and other such online Fandom Influencers have a responsibility to clear up that Bait and Switch, not collaborate with it.

Now since Minerva doesn't take on a Cheetah look till the final battle, and some casual viewers may not instantly know to associate the name of Minerva with Cheetah, perhaps this Minerva becoming Cheetah you can argue is sufficiently a surprise.  But the Tweets I made didn't even say Cheetah, so to such a casual fan all it really gives away is that it's not Black Mask, and again anyone planning to watch this movie as specifically Black Mask fans should know going in that he is even less significant then he was in the Red Hood movie.

You would have to be fairly in the know to get specifically Cheetah from "most overused Wonder Woman villain" which is really only even true in the specific context of Animated DC projects.  Even then exactly what Cheetah is has been inconsistent over the years, I did not give away what kind of Cheetah you'll be getting.

But these DC Animated films are not made for casual fans, they are mostly made for the people who will recognize every obscure name they pull out.  And if Catwoman: Hunted were an exception they wouldn't have been so nonchalant about having a group of Crime Bosses summon Demons, Aliens and Robots to battle in the middle of a film that started as a simple Heist movie.  Even the most fantastical Lupin III movies are not that casual about their fantastical elements.  Only Superhero movies are this all over the place genre wise.