Yes, that. I always feel managers are pressured to make sure devs are worked 8 hours a day, necessarily or not. As for side projects, it is really hard to keep a flow doing that knowing that at any time you may be given a "real task" or a maintenance issue to work on. Maybe contractors have a different work day since they are paid by the hour to do specific things, but full time always have the issue of nothing to do but not being allowed to go home or work on something to enhance knowledge.