Using the Ford app will prioritize SOC, then Departure (precondition) and the truck will start charging before your charge window when needed to achieve the targets. (ie, Your truck will start charging immediately when plugged in if your SOC is really low when you plug in and your EVSE can't get you fully charged in the window with enough time to precondition after SOC target is reached.)
Using the EVSE to schedule your window will force the truck to stay in the charge window and may cause you to miss your SOC target and/or Departure preconditioning since it will not allow the truck to start charging before the window when needed.
If you want to prioritize SOC and Departure - use Ford scheduler
If you want to force the truck to stay in the window - use EVSE scheduler.
I use them in combination. I set the Ford schedule to be my "preferred" charge window. I set my EVSE to exclude the window where my electricity prices are highest. This way, the truck can start earlier if needed, but won't be able to draw during the most expensive window.