If you wanna engage in black-and-white painting and say that there are good stories where spoilers don't matter on the one hand, and bad stories that solely rely on a twist on the other hand, then please be my guest.

Truth is, however, lots of stuff people avoid spoilers of, is in many ways mediocre, and even good works can have strong and weak aspects.

A proper scientific study has to take all of that into account, although I guess you can still proceed from this one for further research.

If you want to deny the role of the surprise element in the enjoyment of fiction as well as story, you're free to do that, too.