I think there some solid reasons why the idea that in RPG play a story is being told hangs around as it does. You have a group of people exploring a shared imaginary space and taking turns deciding (to some extent) what happens next. You also have characters (often heroes and villains no less), and even something that looks a lot like scenes that play out in linear fashion. That all looks a lot like a story. But I don't think those similarities make it so. Perhaps some of the difference might be covered by the difference between story and story telling. The latter might be closer to the truth of what happens at the table. I'll come back to that idea.
The appeal to plot, and its presence or absence often appears in these conversations. We do indeed have some types of RPG play that have a lot of 'plot' preloaded into the GMs prep, and we have others where nothing or only the faintest sketch sits premade. That suggests to me that the activity of roleplaying isn't dependent on pre-plotting (to any extent) but that the activity can support it to some extent. I say to some extent because, first, I feel it's pretty plain that in instances where the GM uses a lot of force to keep the players inside the tracks of the pre-plotted prep that the resulting gameplay is often unsatisfying for some or all of the players involved. Second, I think the sheer number of games that have been designed specifically in part to eliminate this idea of pre-prepped plot suggest that rather a lot of players don't much care for the idea. That said, it's still a very popular style of game. The important point is that while it can be used, it's not necessary.
Admittedly there is a whole lot of nuance between no-prep and massive prep. Things like fronts, or even adventure hooks, are at least plot-ish to some extent. So where does that leave us? I think that actual RPG play contains some story elements but that doesn't actually get us to 'story' proper. So RPG play might be described as similar to story-telling, but not quite the same as even there the participants in collaborative story telling are using their understanding of other stories to craft their elements in turn, but I think it's a stretch to say that RPG players are doing that same thing.