Do I have to spell it out for you?
Yes because you aren’t making sense.
If I had said “Every time they do a full page, something is definitely to happen.” then that is a theory: I would be making a prediction on what will happen given a certain page layout. I’m just saying “I feel that every time they do a full page, something could happen” that is my expectation: a generalized thought about the possibility of something happening given a certain page layout.
In the same way someone could say “Oh you got a good night’s sleep? I’d expect you’ll come in early tomorrow” The connotation is that it could happen or it could not happen but they feel like your behavior is more likely one way. But if they say “Every time you get a good night’s sleep, you'll come in early the next day” The connotation is that they are making a prediction that your behavior is guaranteed. There’s a difference in the words used.
Theories also come up in stories as justifications for the behaviors or story events down the line, but I really hope it was clear I wasn’t doing anything like that.