It's a rebrand + censorship then? I'm not sure the distinction you're trying to make exactly, it's not like Douyin is a completely different thing from Tiktok, so I think "completely separate platforms" is also a stretch. The core technology and parent company/ownership is the same for both.
Its functionally completely separate. Douyin content for people unter 18 its like educational material, science experiments, and pro social content. Tiktok for under 18 in the US is like bikini girls dancing, robot voices reading reddit threads while videos of people playing video games play in the background, and lefty social justice content.
