Not only is that point raised in the theory itself ("The trouble with any attempt by the rebels to do something about the explosion is that the combined mass of the rebel fleet is equal to only a tiny speck of the Death Star's surface."), but the place I've seen that outcome most recently - one of the X-Wing graphic novels - only shows the immediate aftermath of the destruction. Sure, the Rebels made an effort to intercept the debris... but what happened after they realised it was totally impossible to stop the Holocaust?

And even if they did - it wouldn't have helped. Again from the FAQ:

Does it matter whether the bulk of the station was vaporised?

No. Material that is turned to vapour does not vanish. Vapour cools rapidly by radiating its heat to space and also by conducting heat to air once it hits the atmosphere. The result of this cooling is that the vapour would recondense as solid soot, like water precipitating as snowflakes. Indeed the margins of the Death Star II explosion appeared sooty before many of the ground troops noticed the fireball. Therefore some condensation began to occur only seconds after the detonation. In any case the explosion shows numerous large tumbling solid fragments, each of which alone is sufficient to cause a global mass-extinction event. In summary, there are two extreme alternatives, and a mixture of intermediate possiblities in between: (1) big solid chunks of the DS impacting on the surface and throwing up fallout dust; or (2) huge volumes of metallic vapour condensing in the atmosphere to give a similar amount of dust.

And yes, it covers being annihilated into energy (gamma-ray burst) and even being displaced into hyperspace, too.

hS