The standby list has unseated confirmed passengers and standby passengers. Unseated confirmed premium cabin passengers will see their seats assigned from the standby list. Also, most nonrevs do not wear their employee IDs, since doing so both violates the dress code and looks ridiculous.

It is impossible to use the Delta app standby list to determine whether someone assigned a first class seat was a nonrev or unseated confirmed passenger. They're indistinguishable unless you have a screenshot of the standby list before seats were assigned and you know if even one confirmed passenger had been unseated at all.