Not only are you correct, you allowed me to find an equivalent feature in CommonMark! If there is an empty line between some content and its wrapping HTML tags then that content will be interpreted as markdown. So

    <td>
    
    ```js
    console.log("Hello, world!");
    ```
    
    </td>

will work as expected. http://spec.commonmark.org/0.26/#example-118 and further discussion at http://spec.commonmark.org/0.26/#example-153

VSCode's markdown preview renderer ( https://github.com/markdown-it/markdown-it ) implements CommonMark, so I'm very happy right now :)