Okay, let me see if I can explain the difference, as I see it. A combination is a set of moves that can be chained together. A script is how something will happen. So, I can practice jab-cross-hook or jab-slip-close or jab-jab-clinch. Any of those are things that could potentially be used as openings present. A script assumes specific progression, and predicts how things will go, and says "I am the answer if things start this way". So, if someone throws a right haymaker, I'll be able to block it, pass it to my right, step in and apply downward force to shift the shoulders back, step hip-to-hip, and sweep. If we call that a script, we're saying that's how it will go. If we say that is a combo, we're saying that's a chain of movements that flows. It's semantics, but important semantics, because one of the complaints people lodge about some forms is that they present solutions that aren't likely to get to continue the way they are shown, because the other guy won't follow your script. So, if we say those things are scripts, then we have to acknowledge that argument is accurate - the other guy won't follow the script most of the time. But if they're just a way to practice movements that can chain together, then we're not stuck in a script.
It's only different in perspective. I kind of agree with you, except I've had these discussions often enough that I know what folks mean when they call it a script.