In my limited engagement with classified material, where there is an unusually large amount of 'secret stuff' it usually relates to the inexperience of those doing the classifying as opposed to whether or not the actual material needs to be protected by a special classification.
Inexperienced people tend to err on the side of caution.
I recall, with great joy, taking over positions from certain risk averse staff people who had choked the files with 'secrets', and then having a big shredding party within a day or two of going through it all.