While Jin placed the card into his System Driver, he used Bam and Boom in its shield form as a projectile to distract the giant Mecha from firing another blast as it seems like its objective was to kill him. Also, it had already damaged a good portion of the hangar including the valuable items that could be used to be salvaged for analysis.
It would not do any good to Jin's team if it continued to damage any more of the hangar. Unfortunately, the transformation was way too flashy compared to the distraction and the pilot flying the Giant Mecha seems to be veteran enough to know that trouble would be coming if he/she does not stop that blinding light.