They chose the app specifically because its chinese, they still have every other tiktok clone, like clapper (lol), snapchat spotlight, youtube shorts and instagram reels.
Well, its definetely possible on activitypub. Every "app" built on the atprotocol takes data from a relay's firehose and then indexes it and does all the algorithm stuff. There is a project (https://www.fediscovery.org/) that will let people build centralised apps with fediverse data. Although, I could just make an algorithm that looks for keywords a user may be interested in, in the posts database and show it to them, it just wouldn't have every post to its disposal.
I mean, with the fediscovery project, people can make centralised applications from fediverse data (people who opt in) this makes indexing and other stuff that works better centralised possible.
They chose the app specifically because its chinese, they still have every other tiktok clone, like clapper (lol), snapchat spotlight, youtube shorts and instagram reels.