I know what you're saying, and agree for the most part. But, the fire engine at my station uses mostly LED's for it's emergency lights, as well as the interior lighting. The emergency lights are bright, very bright .. but a true spot light has a very focused beam to project it far, yet still very tight, to hold the "spot". I just can't see that LED bulb doing that in that configuration.
Looking at the number of bulbs in that cluster, it would probably be bright enough for the distance (IE from the underside of the truck, to the ground) but the a housing/socket would have to be made/bought, and over-all a cheapo flood light would be a lot less hassle, and ensure that the quality of light is enough for the need.