I think that's great advice, BunnyWantsaPhD, and is something we probably don't think about enough. This might also be something that differentiates a WS for a master's program from that of a PhD program. Maybe I was just lucky, but I felt like for my MA I just wanted to provide the WS that showcased the best, most "polished" form of my writing--not especially in a particular subfield of interest--just something that proved I was capable of doing research at a graduate level.
But with the PhD, I am feeling much more pressure to provide work that begins to show I am capable of the critical analysis and expression of contributing to the field as a scholar. It's not just about organization and coherence now, but also ideas and criticism.