Cait Sith's Regal Gash

So, I've been playing around with this trying to figure out a few things about it. All I've been able to come up with is that is can close Darkness with Shattersoul, which would make it Distortion. Which is Yay for Cait Sith having a BP that can close a t3 SC... But Why Darkness? Or why can't is have it so It can also close Light? (Which would be more fitting for this Avatar.)

Also for a lvl 99 ability, This BP is appalling. Overall, she's only Marginally better than Carbuncle.