Colonial Campaigns Club (CCC)

I've wondered, and maybe it's been discussed before, why do light formations in extended order get the road movement bonus? I think they are already very powerful units. Getting to move in firing formation at the road bonus (especially when movement disruption is used) gives them a huge advantage over regulars. I don't see how the extended formation can utilize road movement bonuses in the real world. I could understand them switching from column to etended order with a lower formation change cost, but not being in column AND extended line simultaneously.