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

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).