Im doing a replay of BD, and decided to use Shedinja for my Team. I trained it to level 30, so it learned shadow sneak. I decided to put it against a Pokemon of the same level and is weak to shedinja. When I used Shadow Sneak, it barely did damage. Appearing as if the STAB affect didnt work. I don’t know if this a change that BDSP made or if I'm doing something wrong. My Shedinjas attack stat has been EV trained, nor does it have an attack weakening nature.
Stab did affect it, its probably because the opposing Pokemon has high defense and shadow sneak is only 40bp.