You clearly understand that there's a difference between the colloquial name and the scientific definition. In the context of the GP comment, the discussion was related to nuts that are poorly named (like peanuts and tree nuts that are actually seeds).
Strawberries aren't berries and tomatoes are. You can say that's wrong all you like, but in the context of how they are botanically classified rather than what we named them you're incorrect.
Imagine if someone said "this chair is an object", and you told them they were wrong, because in Object-Oriented Programming, an "object" is an abstract entity in a computer program, not a thing in the physical world.
They have never heard of object-oriented programming and yet, they're not wrong. You're the one who is wrong by assuming the terms made up by a niche field override common language used by everyone.
> 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.
> as conkers are seeds (not a nut) - so shouldn't be an issue for someone with a nut allergy
I take issue with this, and in fact we can see how the pedantic scientific meaning caused confusion about the actual underlying facts: people with allergies to what are commonly called "nuts" can in fact be allergic to things that according to the pedantic scientific definition are "seeds". So the OP is actually wrong to say it shouldn't be an issue for someone with a nut allergy!
Strawberries aren't berries and tomatoes are. You can say that's wrong all you like, but in the context of how they are botanically classified rather than what we named them you're incorrect.