This has probably come up before, but Au Ra have an appearance modification category called "scales," which can toggle on or off bits of scale including eyebrows for males (and also some sort of black line thing around the eye--no idea what it is).
Without any official confirmation, I wouldn't place much significance on this. A likelier explanation is that they wanted to change things up with a "scales" category when keeping "facial features" would have been more appropriate.
Yet there is little fun in lore if everything is explicitly laid out. These SE designers have been known to put a in a little something, a hint of paprika, to spice up the speculation stew. Sometimes, if a loose thread is visible, it is worthwhile to tug to see if it unravels a curtain obscuring hidden gems.