I am surprised as well.
actually Steem dollars can be redeemed to 1 dollar worth of Steem, making an arbitrage profitable for SBD bought for a lesser price on an the market, to convert to Steem, then repeat.
but it seems there is no way to do the reverse. ( by example converting Steem to receive sbd at a rate of 1sbd=1usd even though they could be sold for more on the market or exchanges )

So is it an anomaly, or will events justify this forecast (new utility for Steem dollars, reintroduction of interest on SBD holding... ?)