Two ground wires from fixture in instructions but only one unattached
This is OK, as the greens on the pendant lights are connected via 1 bare copper to the fixture.
Normally, this would require both of the coppers to come from the same connection point if the shades are metal.
if the shades are non metallic, it would not need the lower ground, but the metal canopy that they hang from needs to be grounded.
Since the mfg. has already bonded the 3 shades, all you need to do is connect your ground to the unused ground and everything will be grounded.
I have found the same instructions with different fixtures because they may be being manufactured in a non English speaking place or what ever your language is I know this site is world wide but colors based on normal North America power.