Earlier quoted context omitted.
The XCode requirement makes some sense because it would take Apple a lot of extra work to port and support their tools on other platforms. Work that they have no incentive to do. But I think the native app market in general has peaked. Most things can be done in a web app now.
The underlying assumption is that Apple is expected to port XCode to some other platform, rather than just using a third party tool on that platform like gcc or VSCode to make iOS apps. Publish a spec and people who want to will make their own tools.
Kind of wish they'd partner with JetBrains and we'd get Apple Studio or something.