When I type /gamerule reducedDebugInfo true to chat in UBUNTU, I still see coordinates etc. On my Windows 8.1 (dual boot on the same machine) it works suffescully and for example commandBlockOutput works in the same world on UBUNTU.

Steps to reproduce:
1) Get Ubuntu (or possibly other linux)
2) Create a world with cheats
3) Set reducedDebugInfo to true
4) Press F3
If you check the gamerule state, it will say that it's true but it will act like if the gamerule didn't even exist.