TYPO3 Core

Following scenario:

website [1] domain.de
default language: German (Base: "/"; de_DE.utf8; de-DE)
additional language: English (Base: "/en/; en_GB.utf8; en-GB; Fallback: "Strict: show only translated content, based on overlays)

website [2] domain.ch
default language: Switzerland (Base: "/"; de_DE.UTF-8; de-DE) - I noticed that this might be wrong in terms of SEO so I wanted to switch it to "de-CH" and "de_CH.UTF-8"
additional language: French (Base: "/fr/; fr_CH.utf8; fr-FR)

website [3] domain.co.nz
default language: English (Base: "/"; en_NZ.utf8; en-GB)

Problem:
I want to use translated news records, event records from website [1] on website [3] (cross-domain, in English) but that's not possible.

To make it work I have to create a "fake" English default language on website [3] which I have to disable so it will look like this:

website [3]
default language (disabled): English (Base: "/"; en_NZ.utf8; en-GB)
additional language: English (Base: "/"; en_NZ.utf8; en-GB)

Now I can use the translated news records from website [1] on website [3].

The same problem appears on website [1] and [2] with German and Switzerland, only there it's not that obvious because Switzerland is also a German speaking country, so using the default language for news records works (besides I have to change ß into ss) manually.

I think the correct way would be to translate the German news to the Switzerland localization and then use the translated news on website [2] but that's not possible because I would need to add German as the default language and disable it as well.

I also noticed that German is not available as language record on the root site [id=0].
Wouldn't it be better to have all available languages for a TYPO3 instance on the root site [id=0]? The you can choose the desired languages for a website in the site configuration and maybe translations cross-domain would work that way? I would imagine that having German as an additional language on another website and then I want to use the German news records wouldn't work too.

In summary:
It should be possible to use a language as the default and an additional language on different websites/domains and use translated records.

Can anyone reproduce and confirm the issue? I don't know if the issue still exists on TYPO3 10.