The PID of many wondercards are random and generate when you receive them (unless it is a fixed event) and thus you can soft reset for different natures, IVs, and even Shiny events.
PID is the random number that determines IVs, Nature, Ability, and if a pokemon is shiny or not. If anything that the PID determines seems to be random while you soft reset (like getting different natures each time) then most likely the PID is random and you can get a shiny with soft resets.