I think this recently changed in the last few years... maybe someone with more insight can comment or correct me.
My understanding is that there is a summer access program.. where coaches can require 8 hours per week of weight training, conditioning and film review (2-hour limit on film) for a maximum of eight weeks. Coaches can attend any these sessions.
Aside from those eight weeks... the programs are considered voluntary workouts. These are the workouts that coaches cannot attend and must be conducted by strength and conditioning coaches.