I totally disagree with him, because a Designer is not an Artist or Programmer to implement the stuffs, just like strategists will never fight in battle field - that is the duty of soldiers (I won't say which one is more important, because WE are a TEAM). The strategist can create mini-battle field in order to show his strategy, but he will never (and shouldn't) actually fight.
Hopefully that just came out poorly worded post and not as your general world view.
In the real world everybody needs to contribute as much as they are able, not just as much as is convenient or whatever matches their job title.
Our designers do design, yes, but they also do so much more. Designers draw up concept art when the concept artists are busy. Designers build prototypes in flash or other tools when nobody else is able to. Our designers record their own voice as placeholder audio when nothing else is available. Designers will act as QA when needed. And our designers have their hands on all kinds of scripting and xml files far beyond what may be thought of as a designer.
Instead of asking "Is this part of my job?", ask yourself instead, "What can I do to bring the best possible game to market?"