As you say, are different concepts, light is interaction with photon particles and electricity is electron energy transfer, but I think the joint reason is for:
1) It is supposed to play RM with no more books, so we have no all those lists in companions. So we need to insert electricity attacks in somewhere for main game.
2) It is supposed a magician should create all elemental attacks, then it is needed a place for it, 'light law' was selected.
Maybe it should be more correct to use the 'wind law', unfortunately the current 'wind law' has no blank space for it.
You could modify the 'wind law' to insert the shock/lightning bolts as in 'light law', removing/reordering some spells in the current 'wind law' spell list, and then modify the 'light law' using the same bolts but with heat criticals as metioned before. But as you can see it is not trivial.
But, if you want an explanation for using electricity attacks in light law, so there is no need to modify all that, think that light can produce electricity, look at solar energy, then a shock/lightning bolt could be interpreted like accumulate light in one point, convert it into electricity energy, and launch it in bolt form, as this conversion is possible (light -> electricity).
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There is another bolt that should be changed definitely, the ice bolt, with the current description I see it as if we take an ice piece of our freezer and throw it to target, for that it uses impact criticals, IMO that interpretation is wrong.
I see the ice bolt like a condensed cold, it has no mass (it can be ignored) like the fire or light bolts, so it should use cold and not impact criticals. Like cold criticals are better than impact (if I remember well) and the bolt has no mass, then secondary critical should be removed.
So, the ice bolt is like the fire bolt but does cold criticals, I think this is the correct interpretation.
