Not necessarily. You can have a tightly integrated system that is not a closed system. There was nothing (technical) preventing Apple from implementing their libraries/framework/graphical frontend on top of a Linux backend. Feel free to correct me if I'm wrong, but this seems more like a business decision (i.e. 'Not invented here' or "We don't control it") and/or license issue (i.e. 'GPL is viral') . (I know that Steve was CEO of NeXT and brought that platform with him and that's what they used, but it wasn't necessary for them to do so.)
I think we're talking about different parts of 'open.'
I'm taking about access (sanctioned and encouraged), for regular users. Basically, the front end. In the backend, low level stuff these things take on a different meaning. You're probably right about the business decision.
In the sense that I'm talking about, Android or ChromeOs may be closed. I'm probably using the wrong words and being confusing, but I think there is a relevancy here.
