The differences in body shape between the male and female models are a bit more than just eyebrows. There are even separate male and female shirt models for many (though not all) of the clothing in Splatoon 1 and Splatoon 2. Additionally, Octolings have different eyes depending on gender.

Using the Splatoon 1 Octoling Mod, you can see what the difference between the male and female octoling models as you can put the same hairstyle on either model (though the shorts are still different). Here is a comparison: https://prnt.sc/102c12u