This is all mentioned in the first three paragraphs of the article btw. Yeah it does seem really wild that Japonic languages and Turkic languages could be from a common origin
I think the debate around it points to an interesting issue in the quest of trying to taxonomize languages. It's a similar problem faced by bacteria and fungi taxonomists. These organisms are extremely prone to horizontal gene transfer (some even use functional horizontal gene transfer as an adaptation strategy to adapt to new environments). Languages can borrow a lot from each other and trying to untangle them is always gonna take a ton of guesswork. But it's also what makes the field so interesting. It forced this type of linguistic work to be very interdisciplinary
I think the debate around it points to an interesting issue in the quest of trying to taxonomize languages. It's a similar problem faced by bacteria and fungi taxonomists. These organisms are extremely prone to horizontal gene transfer (some even use functional horizontal gene transfer as an adaptation strategy to adapt to new environments). Languages can borrow a lot from each other and trying to untangle them is always gonna take a ton of guesswork. But it's also what makes the field so interesting. It forced this type of linguistic work to be very interdisciplinary