Can you debug your runtime (Ruby, Python, the JVM, whatever) in gdb? I can, and I still don't consider myself "full-stack"--both because I leave JavaScript to JavaScript people, but also because if you asked me to debug a kernel I'd look at you and just shrug.
The stack goes down past your application.
So for me that's HTML, CSS (Less/Sass), JS (React, Angular, jQ), on the frontend and then a choice between Node, PHP, Ruby, or Python plus DBMS on the backend depending on the requirements / my mood.
The only bits that really extend beyond that are interfacing with external libraries such as ffmpeg, imagemagick etc.
I've not seen any instances of full-stack implying heavy dev-ps experience for example. And that's in 12 years of pissing my life away being a "full-stack" developer.
Heck, right now I'm employed as a "front-end web developer" and spent last week writing an API-only Node app and configuring TC/Azure deployments and NginX.
Anyway, got a bit off track here... my original point was that "full stack" is pretty well defined and has been for a long time.
The line generally gets drawn at "Does it run on one server?", in my experience.
I suspect if Docker pans out like it wants to that will change though, but perhaps that's my naiivety showing through
But I am a cynic.