I decided to look into that and ended up reading an article on the University of California website, which went and gave away the ending of The Usual Suspects in its second paragraph. I know its their job to share knowledge, but c'mon.
I did my own study a while ago, with a very limited sample size, watching The Usual Suspects and The Sixth Sense for the first time after being spoiled on them and I didn't like either film. I found them really boring. Would that have changed if my first experience of them had been completely blind? I'll never know. I certainly don't have any interest in watching them a second time.
I also spoiled myself on Rise of Skywalker, because I heard that it was terrible, and I ended up enjoying that movie more than a lot of people. I knew what I was getting into, so there was nothing left to disappoint me and I could appreciate it for the flashy mess it was.
So my conclusion is that people enjoy bad things more when they are spoiled, and good things less. And if you think my study is inferior to that study due to the fact it's entirely unscientific and only involves one person, then that's fine. But they didn't study movies at all, only short stories that the people in the test didn't want to read to begin with.