Quick comment, will edit as I analyze the rest.
Let's not mind about the fact that the name of the currency is misleading, since there is no actual dollars backing it.
In fact it is backed by STEEM. Here's how: the reward pool is set and in terms of STEEM. However, for some of the amount it gets converted to SBD instead at price feed rates. When/if that ever gets redeemed back, it gives out STEEM at the price feed rates at redemption time. So it is a deferred STEEM issuance.
It is backed by a set amount of steem at market prices at payout time.
Makes Sense. Would be called Dollar Backed Steem If It were the opposite.
Maybe this is one of the things that create some confusion.