Taking the FlightAware data and the OP together:

The flight left the gate at 12:15 and was scheduled to depart at 12:25. OP's husband arrived at the gate and it was empty with nobody around. This means that he could not have arrived at the gate prior to 12:15 and that would have been 10 minutes late. Thus, he was properly offloaded and has no complaint.

Anything F9 did was a courtesy beyond what was required and OP's husband ought to be grateful. I say this as one who is far from an F9 fan and avoids it when there is an alternative.