In real life the JDAM (and probably other missiles) can have new target information and coordinates reprogrammed inflight either manually by the pilot/aircrew or automatically by the plane’s computers using info from GMTI. This means that these bombs should be able to target moving vehicles when in GMTI.
It’d be a bug report. Forced target designation works for air to ground weapons, even for GMTI, even though no missile in game currently uses it for constant (datalink) operation from that specifically, stuff like the ASM-1/2 use non constant GMTI designation.
This would effectively make JDAMs radar munitions though so I doubt this feature would be added given Gaijin’s lack of will to add new guidance methods.