the ES6 section is a bit harder, and actually have a few things that are explained in later sections, so you can jump over it, and return to it later. Or you could do it now and experience hand on how it is to have to do something completely unknown - you will need to do a lot of research
But is it technically a continuation?
It is a continuation. ES6 is an extension to JS that went into effect in 2015 so it is pretty common now. And it will be very important for things like React.
I would recommend just doing things in order. But, as Leah points out, there are some problems with the ES6 section, and it sometimes refers to things that are taught later. That will be a great chance to work on your research abilities (google, mdn, stack overflow, etc.), and extremely important skill for a dev.