Shadow demons seem to be the only incorporeal creatures that do not have incorporeal touch attacks. Is that on purpose or a mistake? In D&D, it had a special ability that allows its claws to affect corporeal creatures.
Lacking a body, they wouldn't be able to make any claw attacks, except against other incorporeal creatures.
You can consider it a mistake. There is no special ability that allows incorporeal creatures to attack corporeal ones.
An incorporeal creature's attacks pass through (ignore) natural armor, armor, and shields, although deflection bonuses and force effects (such as mage armor) work normally against it.
Seems to indicate that incorporeal attacks can harm corporeal creatures (and ignore most armor and shield bonuses).