That is a compliment. The separation of front end developer and back end developer is obsolete and untrue. Either you are a developer or not. If you work on web, then you must, now or in the future, know how web browsers work, how APIs work, how to write and consume them, etc. The browser is just an API we consume from JS. There are many others.
Node and JS is just an example of how easy it is to write code for the back and front ends. You may employ as much langues as you want like PHP, Java, Rust, Python or even Elixir. Does not matter.