Neither Elspeth, nor any version of Gideon, can be selected as your planeswalker for any of the Nightmare of War matches. I’ve verified that they can be selected for Story Mode and Training Grounds, but they are nowhere on the list (locked or unlocked)
//Edited Title -Brigby
It’s not a bug, just a miscommunicated feature.
The nightmare of War event is a Blue, Red, Green, Black event so no white PW’s allowed.
Ah, yep - missed that detail. It wasn’t listed under the deck restrictions in the sneak peak post, only the set restrictions were. Definitely something that would classify as a restriction, not sure why none of them have the restricted color listed.