Identify the defect?

Modern GE distribution (sub-) panel:
The tie bar has been removed, but the bonding screw is installed in one bus bar (the panel came with one bonding screw but 2 secondary (not supply) bus bars, neither of which is labeled as the neutral, and both have holes labeled “bonding screw”.
Is having the bonding screw installed in either/just the neutral or grounding bus bar a defect?

Since you said that it was a sub-panel then only the EGC bus should be connected to the enclosure so only one screw required.