At DAL the gate agents have always put a JS in FC or the highest class offered if a seat was avail. I have never seen them leave a seat open like that. If that is some policy that has just been adopted by ACS, our JS chair needs a chain of incidents to arm himself with.
Once those cases start coming in he can approach the company and in turn ACS to deal with the issue. Until that time IF this is occurring there will be no one to refute it and the practice will grow.