"And I don't understand why you say that DADGBD is "essentially standard tuning"?"

Because it is essentially standard tuning. I'd never ask for a chord chart for drop-D tuning. It's pretty well understood that every chord you play in standard, you play in drop-D with a compensation for the lower bass string.

Same goes for double-drop-d. Every chord you play in standard, you play in double-drop-d the same way with the high E string covered two frets higher or muted.