What you’re noticing has actually always been a function of the rewards calculations. You’re just noticing it now due to the decline in Steem value.

SBD are actually a debt instrument. If the Steem value decreases, or the supply of SBD grows too much (or both!) the blockchain manages distribution to try and keep the debt level under a certain percentage and sustainable. 

You’re seeing a portion of the SBD side of the 50/50 split paid as liquid Steem to control the debt load. Back in the days when Steem dropped into the .10 range, there was a long stretch where no SBD were paid out at all.