when you install the update your asked to apply player data like when you import a team. this will still give you the boots, ball and kits without defaulting your squads. you would have to create the new players yourself.
i exported all of my created teams, installed the DLC and re-imported, all fine now!
one piece of advice is to delete players in create player section if they are in the squad of the team you exported, otherwise, when you import that squad youll end up with duplicates
Or an easier way is to just say no to overwriting save data when asked, then everything you have done stays the same including created players, no duplicates either!
And you still get the boots and balls etc!