Isn't tiktok's whole thing that it shows you very personally curated content based on data about you including demographics and most users see different content? Wouldn't users from Ukraine and England or ones from Mexico and America also see different videos?
Are the Ukrainian videos actually unavailable in Russian TikTok if you search for them? It seems obvious that as you watch more non-war stuff (which might be the default based on the demographics) you'll see even less of them in the Russian account. And if you really can't see them even if you try (which the article doesn't even say as far as I saw) then isn't that the real news rather than the experiment that just shows how different demographics see different things on TikTok? What am I missing?