When people build gypsum walls around stair enclosures there are an array of issues that can arise. The one that concerns me the most is that you have a head of wall joint and a bottom of wall joint at EVERY floor.
There is no way to get traditional firestop sealants and sprays behind the stair runner.
This means you will have about 18 inches at the top and bottom of the wall on every floor, on each side of the stairs where your firestop will not be installed.
Tomorrow I will explain another reason I don’t like exit shafts made of gypsum board.