Mossy Cobblestone is instead called "Moss Stone", contrary to the Item ID and the Mossy Cobblestone Wall.
Linked issues
duplicates 1
Comments 8
English US: Moss Stone
English, Canada: Mossy Cobblestone
English, United Kingdom: Mossy Cobblestone
English, Austrlia: Mossy Cobble
Forward resolving to MC-73344, in favor of the information provided in that issue.
It's spelt perfectly correct for me in 1.6.1.