This is definitely a concern. I've previously worked for e.g. eye bee... and despite having written massive amounts of code in c, java etc, I'm probably violating some major NDA if I show any of that code, or discuss details of a first-in-the-world active-active HA cluster solution in the 90s.
By comparison, my github or personal code would be just a bunch of perl, rexx, sh/bash and python scripts written just to automate some work. I doubt anybody would think those should be cleanly written, highly maintainable, modularised, etc...