Souness is and was a superb pundit, he talks straight and what he says about Grealish is spot on.Souness is full of shit, Jacks a quality player and similar to when people used to question Gundo, they're failing to see he's performing a specific role in a specific way not necessarily flattering for the player but beneficial to the team.
You argument about specific roles is always used to defend him, yet we have seen from Doku that Pep allows and encourages a player to take chances and take on his man in the final third.
Grealish playing as a wide front man in this team HAS to create and score more.