Sure - but most of Trek continuity is purely accidental anyway. Why choose an interpretation that is contradictory when one can choose a continuity-supporting one with equal ease? I find it particularly enjoyable that Deck 11 in retrospect coincides with torpedo launchers, that antimatter in retrospect coincides with photon torpedoes, and that the VFX accurately pounds the very part of the ship coinciding with the above.
(Although actually the people doing the VFX would be the same guys who did the torp launch VFX, and might be aware of a thing or two, perhaps even deliberately attempting to show the enemy aiming at Kirk's big guns. But I sort of doubt that.).
Too late--Reliant got another shot off before Kirk could get power diverted to the phasers.
But what would be "too late" about that? There would be no reason to abort diverting power to phasers just because Khan squeezed off another shot. In a long series of shots, too: this last one isn't decisive or anything.
And it's not as if firing at Khan would plausibly stop Khan from firing, not when Khan is shielded and all. Not that firing at a torp would stop Khan from firing, either. But at least it would help protect the Enterprise
when shields obviously couldn't accomplish that.