ATP rules and ATP based on Planning

So when a user performs an ATP inquiry and the system is set to planning we made the assumption that yes the inquiry will take into account all planning recommendations for reschedules etc. We also assumed that when you are considering sources of supply or demand that it was only looking at real wip orders or purchase orders. But we are seeing that it takes into account Planned orders and Planned order demand. Is that right? People are finally starting to dig into ATP analysis

Thanks in advance