As you might now, every Greenskin LL has a unique version of Waaagh for their army. Grimgor's increases bonus ap damage by a greater amount, Groms heals a little, Azhags grants fear and terror, Skarsniks adds bonus missile damage and Wurrzags adds some bonus physical resistance.
So far, so green.
However, there is also a so-called Big Waaagh which replaces the regular waaagh effect when a waaagh on campaign is active. Essentially, all it does is raise the bonus melee attack effect from 24 to 40. At least, that's the only effect for all lords except Wurrzag.
Wurrzags Big Waaagh for some reason loses the physical resistance, making it virtually identical to the regular Big Waaagh you get on any generic lord whilst the campaign waaagh is active.
What's up with that? Is it some kind of bug or oversight?