I think the staff my be thinking they want to offer a kid at least 2 years as an upperclassman starter. Which I think is necessary to get the top flight QBs to commit. In the present case, assuming Phillip Sims doesnt beat out McCarron, he will only have one year to start as a senior while McCarron starts 3 years.
They maybe trying to space it out a bit. Obviously if there is a highly touted QB out there who is interested despite the depth at the position - you take him. However, if you are evaluating the current pool of recruits and you dont think they can legitimately challenge those you already have at the position and you cant offer them a significant role for a couple of years, I think you wait a year and really focus on bringing in the 4 or 5 star player that can really change a team.