CSP's offense is a full field offense and considered by many coaches and players to be the most complicated in the NFL. Really hard to judge Hill for being limited to half field reads considering CSP's offense is so complex that offensive players don't suffer from the "sophomore slump" due to it taking a full season for them to get a handle on just the base concepts.
If Hill comes out in preseason and Payton keeps him limited to half-field reads, then yes it is time to sound the alarms. But for now it may be more likely that the half-field reads last season were due to a lack of understanding of offensive concepts as a full time QB for Hill than incompetence.