Exactly that. Purslow sacked the immensely popular Smith in easily the most controversial move of his tenure and replaced him with his pal.
He's taken a bit of a gamble here and he's not about to concede defeat after one game.
While the justification for sacking Smith was that the bad results formed a continuum from the previous season, with Gerrard he will consider this season a fresh slate, especially because it's been his first full preseason.
So unless the dressing room erupts in mutiny and results continue to shock, Gerrard is safe, IMO.