No system is 100% perfect and it obviously thinks it could be a collision, when this situtaion happens, i know i need to resume control of the car or sometimes make the car and the radar point at an angle away from the obstruction. In the same way if a car was to cut infront. I often used to steer toward the car abit so the radar picks up the car.
My civic has more safety systems than my golf did and the golf never used to pickup parked cars but the honda does so if you steering maybe towards it or in abit as the road is narrow it can happen, so i deactivate then resume acc when that situation is cleared.
I do believe it is understanding the parameters it can work under that is the key and this is why fully self driving cars unless they have ai and have every parameter defined and every varible possible, they will not work..