For someone reading the code, instead of seeing a standard free() call they see something else. If they're skimming they won't know what's going on. If they're reading carefully, they'll have to go-to-definiton and learn that _glfwFree() does nothing more than free(). Then why does it exist?

When writing new code, should one write free or _glfwFree().

At least the other functions do something else. I'd recommend removing _glfwFree() as long as it does nothing more than call free(). If it ever needs to do more, then re-add it.