Blizzard don’t care about the Monk class.
This is an Elite PvP set from Legion:
The screenshot attached to this page was posted by yours truly.
As you can see, the entire set was designed to be purple, including the “rope” parts of the armor. But they were so lazy while recoloring this set that they kept the rope of the belt red.
I reported this issue several times both using the in game tool, and on the forums.
It’s been 7 years and it still looks like this.