I should probably just leave this to the owners of your make/model of your saw but I have a 2HP Taiwanese contractor's saw and the motor does jump on startup although yours looks little more severe. However, given the Sawstop's extra safety stuff it could be understandable - more weight to get turning. Mine also jumps a lesser amount when turned off.
The motor is literally suspended by the belt and the weight of the motor tensions it so it isn't surprising that it has more movement than a motor that is rigidly fixed. The motor likely wants to climb up the belt when started until the blade mechanism gets moving.
I'm pretty sure you'll get some good replies from owners but if you don't or aren't happy, contact Sawstop.