Well, the answer to the issue you raised is also implied in the question you pose.
If a person is to invest in bonds, don't do it through mutual funds.It is actually not that hard to buy it directly and the mkt in Treasury issues is quite/very liquid.
On the other hand, apparently the common "investor" as you would imagine him probably will also be a firm believer in the EMH as he does seem to ascribe all sorts of information implicit in the daily variations of the stock price.