Well it seems you are in agreement with me :). I have already implied that getting a web browser or some other user-space application running on a new OS requires writing all the other low-level components you have listed. Otherwise it might as well been a Linux distro, which I'm pleased that it isn't one.

A non-Linux OS is a OS that doesn't use Linux as its kernel. The BSDs, Redox, Haiku, TempleOS, SerenityOS and Fuchsia fall under this category which again also implies that it is done from scratch.