Because the answer is false, modules do not solve the problem of having common/shared template instantiations.

As for the comment about MSVC, it's mostly off topic, doesn't relate to the question that was asked (which had nothing to do with which compiler provides the best experience), and even if you accept that MSVC provides the best module experience, it's support for it is still very buggy and not suitable for anything other than experimenting and beta testing.