The Ogre Zombie (Monster Manual, pg. 316) has a morningstar listed as its weapon for attack actions.
However, the damage is listed as bludgeoning damage as opposed to piercing damage (PHB, pg. 149).
It this mentioned in any errata anywhere, or is there any other reason why these morningstars behave differently?
As an extra note, I've always assumed that, if it makes narrative sense, a DM can swap out some weapons for others, so I could have an Ogre Zombie with a Warhammer if I wanted, but generally AFAIK the "default" weapons that creatures have is usually consistent with the PHB weapons...