Because when we will see the reports we can clearly relate the Collison in our mind that what will be happened at site, if both objects will clash during erection at any point but if only an individual object which comes in the first contacts with other objects will appears in reports we can not visualize the intensity.

Example: if an equipment clashing with structure during erection but at the point of contact. it is obvious that first contact will some of the components of the equipment, let say the first contact part is some kind of bolt/nut, it means in reports it will show only nut/bolt that will not show the intensity of disaster which is going to happen during Collison.

Hence, we need complete equipment in reports during clashing with structure.