Flow Control is dictated by ATC in Washington, DC. It tells the airlines what the flow rate is, for how long and if any ground stops will affect the airport--ATC does not tell companies which flights to delay, in what order, what flights to cancel, what flights to divert--that is all Operations Control Center's job.

In the above situation, the case with the OP has many possible answers:

1. No available crew/missing crew (because they timed out, they are on another plane inbound to ATL, etc.)

2. Landing curfews at destination

3. Crew positioning for the next day (rest legalities).

4. Other operational issues that are generally internal.

Compensation will not be given in this situation because Flow Control program is dictated to DL and DL has no control over arrival and departure rates at the affected city.