Well, it's more than just OpenGL bindings mostly because it's bindings for a bazillion other things too. Just look at the javadoc[0]. The non-binding stuff in there is just utilities to make the bindings at least somewhat idiomatic in Java. In practice, LWJGL games are almost always just GLFW games, which I would still qualify as being pretty damn close to "from scratch".
It is indeed a bit like using SDL, however pure OpenGL bindings like JOGL have seen better days.
Also, if you are doing a game in Java, you also need bindings for sound APIs, and other ones that traditionally only care about C, thus you end up with something like LWJGL anyway.
0. https://javadoc.lwjgl.org