It's difficult to tell with the official EA eyelashes from Lovestruck and the BG update but their thumbnails include the standard eyelashes as well.
This is much more apparent on CC eyelashes that deviate from the standard colour choices as they can be seen clipping through the brown looking EA lashes inlcuded in the thumbnails.
You can see in the screenshot that the official lashes worn by my Sim are thinner than they appear in the thumbnail because the thumbnail includes the standard lashes. The thumbnails of the CC lashes make the issue more obvious.
The thumbnails for the EA lashes were generated before I ever added any CC lashes to my game.
