According to the actual behavior of Joplin (and the GFM specification), the following code will result in the behavior of two blocks of quotes.
> Kent.
> Where's the king?
> Gent.
> Contending with the
> fretful elements
But the Markdown Guide on your site is a little misleading, it looks like it's going to be a single block. Moreover, not only does it look, judging by the page code, both quotes are really in one blockquote.