Gamma-Delta was due to Delta already being in use. It *should* have been Gamma, then Delta *now*, but, it didn't fall out that way, so, we'll have those two flipped for a while.
I used Gamma to try and get us at least lined up in terminology, even if it goes, in essence, "A, B, D, C," at this point.
*grumble*
Nothing I could have done on THAT front, Delta's been around for, what, fifteen years now?