It could also be, that since SBD is marked in parts of bitcoin, that since bitcoin is going up so fast, it is taking SBD with it. As, on the bittrex chart shown, if SBD goes sideways, then it is increasing in US$s.
But, that doesn't hold when looking at the long term chart.
I feel that your theory is a better explanation seeing the pump bars in the chart. (large, tall, green candles you see with lots of volume, for those of you who do not know)
On a side note, is bittrex felt to be solid now? As a decent place to leave some of your coins for trading?
I leave some there, but not too much.