And indeed, that is true in many instances.
It is not true, however, in all. Take, for instance, the mainstream trend of creating "bromanteaus." As ozy writes at No Seriously What About Teh Menz (NSWATM):
"Think about nurses: we assume that nurses are female, so if there’s a dude who’s a nurse we might describe him as a 'male nurse,' while 'female nurse' sounds bizarrely redundant. The male nurse is a marked case. Bromanteaus embed the marked case in the structure of the word. Women don’t have 'guyliner,' they just have makeup. Women don’t have 'bromances,' they just have best friends. Women don’t have 'mancaves,' they just have rooms."
Recently, I was in a drug store buying lotion. I reached into the basket of lotions on display and the first one I grabbed was a blue and white bottle of fragrance-free lotion with the word "Men's" on it. It was identical to the gender-neutral bottle in every other way, and it contained the exact same ingredients.
The implication was that women were the usual consumer of lotions, which may indeed be the case, and that it was therefore unnecessary to include the word "Women's" on the bottles that did not include a gender. I was also struck by how rare it felt to be looking at a product that treated me, a woman, as the Default Consumer. Unless a product is pink, a cosmetic, baby stuff, or cleaning stuff, this doesn't seem to happen all that much.
Yet, there was another, more problematic, implication working here, and it's one that works in the above "bromanteaus" as well. That implication is that men won't buy things that women usually buy because they don't want to be marked with the taint of femininity and/or feminine inferiority.
Men can't just say they're putting on eyeliner, because that's what women do. So, people make it a little more acceptable by calling it "guyliner." Even if it's the exact same process and product.
Just another interesting way that artificial gender distinctions are created and maintained.