This, note that the calculations will be simplified. not calculating stuff like turret placement and probably not settler firepower.
its also probably that they are bugged.
Fun story from Skyrim, I and Lydia entered an tower with two powerful mages at low level. Lydia was hit two times and went down. I was next to the door, was hit once and exited the load door. I healed up and waited some seconds not knowing that Skyrim enemies rarely followed trough load doors.
Lydia exits after less than 10 seconds, we enter and I found she had killed the mages, fight was auto calculated and as she could not die she would obviously win, however as the mages could knock her down in seconds it would have been an very long fight. Lydia also took an detour once to avoid jumping down an 1 meter edge and killed an boss while doing so 