We typically find all of the rear valance to taillight panel screws installed. in my observations I found each would have been tightened since they didn't go back and tighten them again after the paint process. Tightening them later would produce cracked and chipped paint that could lead to rust developing not something I've found on original paint cars from this plant and time period
Without the lower stud installed nor pulled into (secured) the unibody the valance still will hang away from the body enough for the spray to wrap around the edges and not fill the gap as it could if pulled tightly at that point against the unibody
Hope this helps
