I think PCB DESIGN meaning Board Design - design the curcuit itself, and PCB LAYOUT meaning tha layout of the board. Ususally those are two different engineers.
PCB design means schematic entry, assigning part properties etc.
Layout has to do with placement, routing and other issues such as gnd ans power planes, high speed design, signal integrity etc. The last one of cource can be another specializer area.
I feel you should know and be aware of both and specialize in any one. This will automatically happen with exp.