At the moment, you're absolutely right!

I have been watching this, as well... and it seems that whenever the markets are "hot" on high volume the SBD to dollar peg goes off kilter. When trading volume drops and the markets are quiet (like they were earlier this week) SBD seems to drop back towards parity with dollars.

Earlier this week when things were "quiet" SBD dropped to about $1.30... last time we had a price spike in Steem, it ran up to $2.12; at the moment we have high volume and strong Steem pricing... and SBD is back near $2.00.