> I get the point that we call them berries even if they aren't
That wasn’t the point. The point is that they are berries, by the real definition of berries, which is not the different definition used by a tiny minority of mostly irrelevant people in a specific context.
What reason is there to prefer the botanical definition to the common one (that says a berry is a small colorful fruit)? I can see none. On the other hand, I can see many reasons to prefer the common definition: it is older, it is used by far more people, and it more closely corresponds to what we care about in real life (because almost everyone spends more time preparing and eating meals than they do classifying plant parts, so the culinary meaning is more important).
Scientists are not in charge of the whole human experience. They do not get to decide on behalf of everyone else that the salient defining characteristic of berries is not how they taste or what dishes you would use them to prepare, but rather what part of the plant they come from.