I"m not sure if this changed in 2013 - If I've got an assembly open which contains subassemblies, and in the graphics window I select a component (part) within a subassembly and delete it, it gets deleted from the subassembly. If I open that subassembly, the component is gone.
I don't recall that - I seem to remember that the same action would delete the subassembly containing the part, not the part itself, but I was also out of work for 10 weeks and using 2011 in my previous job, so maybe I'm wrong?
I looked for a setting to control this & didn't find one. Am I nuts - did this change?