I still don't know how they can have 2 pins next to each other on an SOO8 package having large voltages on them
Because it takes many kilovolts to jump a gap that size. If there's a transient on the mains line, it may arc from one of the pins to another, but that's actually not particularly common.
Also, the separation between the control (low-voltage) side and the controlled (high-voltage) side is bigger than the separation between the controlled (both high voltage) areas. And it's a 120V part, not a 240V part. (still, I might have run that lead under the package a little further away from the 120V if I could.)