Interesting catch, Paul. If you look at the plan itself (E*Trade Commission-Free ETFs) there aren't a lot of fixed income options available in the list and all of them seem to be international. So, the first point here is that it's tough to get a truly low-risk, low correlation instrument within this list.

The chinese yuan is an edge case (ie. we don't classify it well because it's currently outside the granularity of our framework - that will change), but if you think about it, probably not a bad choice. The yuan is pegged to the U.S. dollar and has a return (unlike US money market).

So simply, yuan is being used as a U.S. fixed income proxy in this case. The benchmark for the conservative models is about 40% bonds, 60% stocks.

Tell you what you can do - subscribe to the model and add a U.S. treasury ETF (eg. TLT) to the list...then re-run the models. My hunch is you'll find it heavily weighted in the models.