> "Same or trivially derived" is just a completely false statement

You'd have to ignore a lot of reality to believe this. It's even in the names of the writing systems: Kanji, Hanja, Chữ Hán. Of course they don't exchange, because they don't carry the same meaning, just as the word "chat" means completely different things in French and English. But it is literally the same script, albeit with numerous stylistic differences and simplified forms.

CJK native speakers can't read or write other "trivially derived" versions of Hanzi. I don't understand why this has to be reiterated ad infinitum.

We can't actually read Simplified Chinese as a native Japanese just like French speakers can't exactly read Cyrillic, only recognize some of it. Therefore those are different alphabet sets. Simple as that.

The "trivially derived different styles" justification assumes that to be false, that native users of all 3 major styles of Hanzi can write, at least read, the other two styles without issues. That is not true.

Итъс а реал проблем то бе cонстантлй пресентед wитҳ чараcтерс тҳат И жуст cанът реад он тҳе гроунд тҳат тҳейъре "саме".

I hope you don't get offended by the line before this, because that's "same" latin, isn't it?