It probably doesn't, as you practically never need Xcode for simple apps. From my experience, currently, you need Xcode to compile storyboards (NIB/XIB files) and bundle Assets.car (macOS BOM files); and compile Xcode projects, btw. I may be missing another important feature used in a lot of apps but otherwise for the most part you can build an iOS app without Xcode (or even macOS).

The command line tools are still XCode, in a way.

I am not talking about XCode command line tools. I am talking about currently available open-source tools that can actually replace those command line tools. I don't think that would count as Xcode as those tools are available on systems Xcode can't run on.

Is that true? What about the command-line version?

The Command Line Tools doesn't include the iOS SDK; or a simulator; or any of the other tools required to get it deployed to actual device.