OK, you must be talking about V1.

"Eyelashes" and "EyeLashes = This is an artifact. the one at the bottom of the list has not actual material, it is redundant - DAZ made a mistake when they did the V2P4 geometry and changed the case on two material names. The old names just came along for the ride.
MATposes with the alternate material will paste that material into your cr2 file, even if the actual geometry has nothing for it to texture.

So, No, this has nothing to do with it.

There are eight because the lashes have two layers.
If you only do transmaps for four of the eight, the lashes will be thinner.

Eyes
At the bottom you have sclera, iris, pupil
These are materials with actual substance.
At the top right you have a cornea layer.
This one is supposed to be 100% transparent and is there to provide light refections, so that a texture for the iris/pupils does not need, nor should it have white highlight inclusions.