Using `extern template` to prevent implicit instantiation of a template class

Consider the following code snippet:

template <typename>
struct X { };

extern template struct X<int>;

int main()
{
    X<int>{};
}

It compiles and links: live example on godbolt.org. I would expect it not to link due to the extern template declaration.

My understanding is that extern template means: "please don't instantiate this particular template specialization in this TU, it will be provided by some other TU and you can link against it".

The examples/descriptions. I've seen on isocpp and cppreference seem to validate my mental model. E.g.

From https://en.cppreference.com/w/cpp/language/class_template:

An explicit instantiation declaration (an extern template) skips implicit instantiation step: the code that would otherwise cause an implicit instantiation instead uses the explicit instantiation definition provided elsewhere (resulting in link errors if no such instantiation exists). This can be used to reduce compilation times by explicitly declaring a template instantiation in all but one of the source files using it, and explicitly defining it in the remaining file.

Why does my code snippet link? What is actually happening here?

---

EDIT - found this in the latest Standard draft:

[temp.explicit]

If an entity is the subject of both an explicit instantiation declaration and an explicit instantiation definition in the same translation unit, the definition shall follow the declaration. An entity that is the subject of an explicit instantiation declaration and that is also used in a way that would otherwise cause an implicit instantiation in the translation unit shall be the subject of an explicit instantiation definition somewhere in the program; otherwise the program is ill-formed, no diagnostic required.

Does this mean that the code snippet I posted is ill-formed, NDR?