I know there is no SBD paid out right now, but no US dollar either. Authors and curators receive STEEM only, but the reward is shown in $. The Steem that is paid out is in US dollar terms worth less than the $ amount shown.

If you multiply the amount of Steem that is paid out for a post by the current price of Steem in US dollar it is currently less than the reward that is shown on steemit.com. A post that shows a reward of $10 currently distributes an amount of Steem that is worth about 10 SBD.

Edit: This is only true if the liquid steem ratio remains at 100%. Therefore, I think you are correct it is better not to show the rewards in my chart in SBD, but in $ (the same as on steemit.com).