I'm not saying this is fact, I'm no Logic fanboy, but
I was reading through some posts on the farm, a while back, where Logic claimed that he was in Spain working with some dudes there, brought over his genetics including ChemD and forum cut GSC.
He made that cross and his partners turned around and robbed him of his seeds.
He had to leave Spain broke and then his ex partners started Mamiko Seeds.
It makes since to considering Mamiko doesn't make those seeds anymore, even though it was their flagship strain. Instead, they offer Trainwreck, Sour D, Casey Jones and various Afghan, Og crosses.
It makes sense to me, I don't think they ever had the Chem D cut and they can't get it, to recreate something they stole.