Have you tried exactly the gacha with Shion Aster/Iberis/Texas Bluebell?
It may be because it was added together with the NG premium, that the rates became weird.
As I'm saying, it's only speculation. Then again you must agree that it is really unusual for anybody to have such rolls twice, back to back.
I plan on doing one last 10+1 pull later today (83 FG left), just to check if the gacha rates are really bugged.
I'll report my findings then.