There are still some blocks not added to the /Fill commands list like, Coarse Dirt and probably another, sorry if this wastes your time, just wanted to put out that there are somethings that need to be added. Please and Thank You.
-Sincerely Asher 🙂
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Coarse dirt is dirt with a data value of 1. /fill <x y z> <x y z> dirt 1.